ve equ's.
; 8-28-85: modified morhdc.a86 morrow hard disk controller driver.
; 9-6-85:  added vcsbuf equ for virtual console screen buffers.
; 10-15-85: fixed error print-out.
; 10-22-85: made local stack for disk routines.
; 10-31-85: put in support for Otari C-526 hard disk.
; 11-20-85:  changed to allow up to 12 logical hard disk drives.
; 12-13-85:  made two separate step rates for 5-inch and 8-inch.
; 01-26-86:  support for ADES controller with 33 meg PRIAM hard disk.

true	equ	-1		; value of0		; disk time-out time in seconds.
nflop8	equ	2		; number of 8-inch floppy drives.
nflop5	equ	2		; number of 5-inch floppy drives.
nhard	equ	8		; number of logical hard disk drives.
morrow	equ	false		; true for Morrow hard disk controller.
teletek	equ	true		; true for Teletek hard disk controller.
ades	equ	true		; true for ADES hard disk controller.
rms12	equ	false		; true for RMS-12 hard disk.
cmi19	equ	false		; true for CMI-19 hard disk.
rod20	equ	false		; true for Rodime-20 hard disk.
min20	eq; Drive L.
	if nhard le 7! drivel equ 0ffh! endif
	if nhard gt 8! drivem equ 16! endif	; Drive M.
	if nhard le 8! drivem equ 0ffh! endif
	if nhard gt 9! driven equ 17! endif	; Drive N.
	if nhard le 9! driven equ 0ffh! endif
	if nhard gt 10! driveo equ 18! endif	; Drive O.
	if nhard le 10! driveo equ 0ffh! endif
	if nhard gt 11! drivep equ 19! endif	; Drive P.
	if nhard le 11! drivep equ 0ffh! endif


	; define disk control variables for system.

hlab	equ	8		; fdc head load: 8=before, 0=after, ready.
lpttbe	equ	04h		; transmit buffer empty mask.
lptrda	equ	01h		; receive data available mask.
lbaud	equ	0bh		; Baud Rate:  b=9600, c=19200.

	; Serial Port Board Addresses and Mask Bytes.
	; Currently set up for 2 Tarbell 4S/2P Boards.

spbase	equ	0		; board starting address.
spimsk	equ	2		; input status mask.
	if	not dtrcon	; if no dtr handshaking on console.
spomsk	equ	1		; output status mask.
	endif
	if	dtrcon		; if dtr handshaking on console.
spomsk	equ	81h		; output status mask.
	e true for assembler.
false	equ	not true	; value of false for assembler.

	; Console options.
conint	equ	false		; true for console interrupts.
cibmax	equ	20		; console input buffer maximum characters.
nvirt0	equ	1		; number of virtual consoles on console 0.
nvirt1	equ	0		; number of virtual consoles on console 1.
nvirt2	equ	0		; number of virtual consoles on console 2.
nvirt3	equ	0		; number of virtual consoles on console 3.
nvirt4	equ	0		; number of virtual consoles on console 4.
nvirt5	equ	0		; u	false		; true for Miniscribe 4020.
ota26	equ	false		; true for Otari C-526 hard disk.
ats33	equ	true		; true for Atasi 33 hard disk.
q540	equ	false		; true for Quantum Q540.

	; define which drives are 8-inch and which are 5-inch.
	; 5-inch floppy drives are numbered 0-3, 8-inch from 4-7.
	; Hard disk drives are numbered from 8-19.
	; Undefined drive letters are numbered 0ffh.

	if	not mini	; for booting on 8-inch drives.
drivea	equ	4		; drive a is 8-inch drive 0.
driveb	equ	5		; drive b is 8-seek.
pctrk	equ	43		; pre-compensation above this track.
ibmtpd	equ	40		; ibm tracks per 5-inch floppy.
rtcnt	equ	10		; fdc read/write, fail retry count.
srtcnt	equ	2		; fdc seek retry count.
pcsbas	equ	0f000h		; 80186 peripheral ports base address.


	; Virtual Control Keys.
	; These are the codes for the keyboard keys that cause
	; switching to another virtual console.

vkey0	equ	1ch	; ctl \ - go to virtual console 0.
vkey1	equ	1dh	; ctl ] - go to virtual console 1.
vkey2	equ	1eh	; ctl ^ - gndif

	; Auxilliary Port Addresses.

	if	not vio		; aux is on Tarbell 4S/2P.
auxist	equ	spbase+7	; aux in status port.
auxin	equ	spbase+6	; aux in data port.
auxost	equ	spbase+7	; aux out status port.
auxout	equ	spbase+6	; aux out data port.
auximk	equ	spimsk		; aux in mask.
auxomk	equ	spomsk		; aux out mask.
	endif

	if	vio		; aux is first port on Duplex 816.
auxist	equ	pcsbas+182h
auxin	equ	auxist+4
auxost	equ	auxist
auxout	equ	auxin
auximk	equ	1
auxomk	equ	4
	endif

	; Floppy disk cnumber of virtual consoles on console 5.
nvirt6	equ	0		; number of virtual consoles on console 6.
nvirt7	equ	0		; number of virtual consoles on console 7.
ncrts	equ	1		; number of physical crt consoles.
nvirt	equ	nvirt0+nvirt1+nvirt2+nvirt3+nvirt4+nvirt5+nvirt6+nvirt7
vcsbuf	equ	false		; true if virtual console screen buffers.

nptrs	equ	1		; number of printers.
stprat8	equ	0		; 8" step rate: 0=3ms, 1=6ms, 2=10ms, 3=20ms.
stprat5	equ	1		; 5" step rate: 0=6ms, 1=12ms, 2=20ms, 3=40ms.
nsio	equ	0		; inch drive 1.
drivec	equ	0		; drive c is 5-inch drive 0.
drived	equ	1		; drive d is 5-inch drive 1.
	endif

	if	mini		; for booting on 5-inch drives.
drivea	equ	0		; drive a is 5-inch drive 0.
driveb	equ	1		; drive b is 5-inch drive 1.
drivec	equ	4		; drive c is 8-inch drive 0.
drived	equ	5		; drive d is 8-inch drive 1.
	endif

	; Hard Disk Drives.

	if nhard gt 0! drivee equ 8! endif	; Drive E.
	if nhard le 0! drivee equ 0ffh! endif
	if nhard gt 1! drivef equ 9! endif	; Drive F.
	if nhard o to virtual console 2.
vkey3	equ	1fh	; ctl _ - go to virtual console 3.


	; console port addresses and mask bytes.

	if	not vio		; console is Duplex 816 first port.
cbase	equ	pcsbas+180h	; port base address.
condat	equ	cbase+06h	; data port.
consts	equ	cbase+02h	; status port.
contbe	equ	04h		; transmit buffer empty mask.
conrda	equ	01h		; receive data available mask.
	endif

	if	vio		; console is Fulcrum VIO video board.
cbase	equ	0
condat	equ	cbase+1
consts	equ	cbase
contbe	equ	1
conr	dmabas+04h	; destination pointer lower.
dmaspu0	equ	dmabas+02h	; source pointer upper.
dmaspl0	equ	dmabas		; source pointer lower.
fdmard	equ	0a266h		; floppy-to-memory command.
fdmawt	equ	016a6h		; memory-to-floppy command.

	; 80186 Timer Ports and Constants.

timbas	equ	pcsbas+0f50h	; timer base address.
timct0	equ	timbas		; timer 0 count register.
timca0	equ	timbas+02h	; timer 0 max count register a.
timcb0	equ	timbas+04h	; timer 0 max count register b.
timmc0	equ	timbas+06h	; timer 0 mode/rd ptr .38H
mpmseg		equ	ds: word ptr .40H
endseg		equ	ds: word ptr .44H
rlr		equ	ds: word ptr .68H
thrdrt		equ	ds: word ptr .72H
qlr		equ	ds: word ptr .74H

version		equ	ds: word ptr .78H
vernum		equ	ds: word ptr .7AH
mpmvernum	equ	ds: word ptr .7CH
tod		equ	ds: byte ptr .7EH

open_vector	equ	ds: word ptr .88H

;*********************************************************************
;* end of system data area definition
;*********************************************************************

dph12! endif	; drive I.
		if nhard le 4! dw 0! endif
		if nhard gt 5! dw offset dph13! endif	; drive J.
		if nhard le 5! dw 0! endif
		if nhard gt 6! dw offset dph14! endif	; drive K.
		if nhard le 6! dw 0! endif
		if nhard gt 7! dw offset dph15! endif	; drive L.
		if nhard le 7! dw 0! endif
		if nhard gt 8! dw offset dph16! endif	; drive M.
		if nhard le 8! dw 0! endif
		if nhard gt 9! dw offset dph17! endif	; drive N.
		if nhard le 9! dw 0! endif
		if nhard gt 10! dw offset dph18! endif	; drivdw	io_auxout	; 6 - aux out.
	dw	io_switch	; 7 - switch screen.
	dw	io_statline	; 8 - display status line.
	dw	io_seldsk	; 9 - select disk.
	dw	io_read		;10 - read sector.
	dw	io_write	;11 - write sector.
	dw	io_flushbuf	;12 - flush buffer.
	dw	io_poll		;13 - poll device.
	dw	io_ret		;14 - dummy return.
	dw	io_ret		;15 - dummy return.
	dw	io_ret		;16 - dummy return.
	dw	ww_key		;17 - wait for a key.
	dw	io_ret		;18 - dummy return.
	dw	io_ret		;19 - dummy return.
	dw	io_ret		;20 - dummy return.
control word.
timcnt	equ	33340		; max count for 16 milliseconds.
timbeg	equ	0e001h		; code to begin timer.

	; 80186 Interrupt Controller Ports.

intbas	equ	pcsbas+0f20h	; interrupt port base.
inteoi	equ	intbas+02h	; eoi register.
intmsk	equ	intbas+08h	; mask register.
inttcr	equ	intbas+12h	; timer interrupt control register.
intcr1	equ	intbas+1ah	; int1 (8259) interrupt control register.

	; 8259 Interrupt Controller Ports.

inta0	equ	pcsbas		; input a0 = 0.
inta1	equ	pcsbas+2	; input a0 = 1

;
; XIOS Header Definition
;

	cseg
	org	0c00h

	jmp	init		; system initialization.
	jmp	entry		; xios entry point.

sysdat		dw	0		; Sysdat Segment.
supervisor	rw	2

	dseg
	org	0c0ch

tick		db	clock		; tick enable flag.
ticks_sec	db	60		; # of ticks per second.
door		db	0		; global drive door open.

rsvd		db	0		; reserved for operating system.

npcns		db	ncrts		; number of physical consoles.
nvcns		db	nvirt		; number of virtual consoles.
nccb		db	nvirt		; total number of ccbs.
ne O.
		if nhard le 10! dw 0! endif
		if nhard gt 11! dw offset dph19! endif	; drive P.
		if nhard le 11! dw 0! endif

alloc		dw	0

	; Console Characteristic Table.
	; This section may be written into by an INSTALL program,
	; as it is always at the same offset relative to DS.
	; For sequences, first byte is number of characters
	; in sequence.  If most significant bit of first byte
	; is set, that means column comes before row.
	; Any other byte with bit 7 set means add cursor
	; position or o
	dw	io_ret		;21 - dummy return.
	dw	io_ret		;22 - dummy return.
	dw	io_ret		;23 - dummy return.
	dw	io_ret		;24 - dummy return.
	dw	io_ret		;25 - dummy return.
	dw	io_ret		;26 - dummy return.
	dw	io_ret		;27 - dummy return.
	dw	io_ret		;28 - dummy return.
	dw	io_ret		;29 - dummy return.
	dw	io_screen	;30 - get/set screen mode.
	dw	io_video	;31 - video i/o.
	dw	io_keybd	;32 - keyboard info.
	dw	io_shft		;33 - shift status.
	dw	io_eqck		;34 - equipment check.
	dw	io_int13_read	;35 - read DOS di.

	; additional system equates.

fresh	equ	1		; bdos fresh disk access bit mask.
ticflg	equ	1		; 1/n system interrupt tick flag.
secflg	equ	2		; 1 second interrupt flag.
flgset	equ	133		; xdos code to set flag.

	; Standard ASCII CRT codes.

cr	equ	0dh		; carriage return.
lf	equ	0ah		; line feed.
bs	equ	08h		; back space.
bel	equ	07h		; bell.
esc	equ	1bh		; escape.

;
psh	equ	byte ptr 15	; physical sector shift position.

	; define address refs for system.

bdos_int equ	224		; reservelst		db	nptrs		; number of list devices.

ccb		dw	offset ccb0	; offset of first ccb.
lcb		dw	offset lcb0	; offset of first lcb.

			; disk parameter header offset table.
			; for dphx, x = 0-3 for 5-inch,
			;	    x = 4-7 for 8-inch,
			;	    x = 8-15 for hard disk.

dph_tbl		equ	offset $

		if	not mini	; for booting on 8-inch drive.
		dw	offset dph4	; drive A.
		dw	offset dph5	; drive B.
		dw	offset dph0	; drive C.
		dw	offset dph1	; drive D.
		endif

		if	mini		; for booting on 5-inch dther variable for code to send.
	; Table shown here is for Televideo 910+ CRT.

	; maxcol, maxrow determine maximum screen size.
maxcol	equ	80			; maximum number of columns.
maxrow	equ	24			; maximum number of rows.

	; actual table starts here.
nocols	db	maxcol			; number of columns.
norows	db	maxrow			; number of rows.
nochrs	dw	maxcol * maxrow		; number of characters.
inslin	db	02h,esc,'E',00h		; insert line at cursor.
dellin	db	02h,esc,'R',00h		; delete line at cursor.
setdim	db	02h,esc,')'sk.
	dw	io_int13_write	;36 - write DOS disk.

initof	equ	offset $
	cseg
	org	initof

	; *********************************************************
	; ******************* cold-start entry ********************
	; *********************************************************


init:

	; initialize system.

	cli				; disable interrupts during ini.
	mov	sysdat,ds		; save sysdat for sysdat access.
	mov	ax,supmod		; place copy of SUPMOD in data seg.
	mov	supervisor,ax		; into code segment (supervisord bdos interrupt.
ovec1	equ	1 * 4		; SID's interrupt vector.
svec1	equ	ovec1 + 2
ovec3	equ	3 * 4
svec3	equ	ovec3 + 2
ovece1	equ	0e1h * 4
svece1	equ	ovece1 + 2
ovece6	equ	0e6h * 4		; int e6 address.
svece6	equ	ovece6 + 2
p_uda	equ	word ptr 010h		; pd uda segment adr.



;*********************************************************************
;* sysdat for a RASM86 system.
;*********************************************************************

supmod		equ	ds: word ptr .0H
dispatcher	equ	cs: worive.
		dw	offset dph0	; drive a.
		dw	offset dph1	; drive b.
		dw	offset dph4	; drive c.
		dw	offset dph5	; drive d.
		endif

		; Hard Disk Drives.

		if nhard gt 0! dw offset dph8! endif	; Drive E.
		if nhard le 0! dw 0! endif
		if nhard gt 1! dw offset dph9! endif	; drive F.
		if nhard le 1! dw 0! endif
		if nhard gt 2! dw offset dph10! endif	; drive G.
		if nhard le 2! dw 0! endif
		if nhard gt 3! dw offset dph11! endif	; drive H.
		if nhard le 3! dw 0! endif
		if nhard gt 4! dw offset ,00h		; set intensity to dim.
setbrt	db	02h,esc,'(',00h		; set intensity to bright.
clreos	db	02h,esc,'Y',00h		; clear to end of screen.
setcur	db	04h,esc,'=',0A0h	; load (set) cursor position.
	db	0A0h,00h,00h,00h
	db	0ffh			; marks end of modifiable space.


;
; XIOS Function Table.
;

functab	dw	io_const	; 0 - console status.
	dw	io_conin	; 1 - console input.
	dw	io_conout	; 2 - console output.
	dw	io_listst	; 3 - list status.
	dw	io_list		; 4 - list output.
	dw	io_auxin	; 5 - aux in.
	 debug
	mov	int0_offset,(offset int_trap)	; set int 0 vector.
	mov	int0_segment,cs
	mov	di,4			; start at int 1.
	mov	si,0			; come from int 0.
	mov	cx,510			; do rest of 255 int's.
	rep	movsw			; write em out.

	mov	word ptr .0008h,offset nmiint	; set nmi.
	mov	word ptr .000ah,cs

	endif				; end debug conditional.

	; set e6 interrupt vector.
	mov	ax,offset xios_v1_entry
	mov	es:word ptr .ovece6,ax
	mov	ax,cs
	mov	es:word ptr .svece6,ax

	if	clock			; if tick interrupt.

	; set timer  port on Duplex 816.
	mov	dx,lbase		; port for data format.
	mov	al,13h			; char, no parity,
	out	dx,al
	mov	al,07h			; 8 data bits, 1 stop bit.
	out	dx,al

	mov	dx,lptsts		; get clock select port.
	mov	al,(lbaud shl 4)+lbaud	; get baud rate code.
	out	dx,al			; set baud rate.

	mov	dx,lptcom		; get command port.
	mov	al,45h			; reset errors, enable.
	out	dx,al

	if	nsio gt 0		; if 1 or more 4S/2P ports.

	; Initialize 4S/2P Serial Ports.
	mov	dx,spbase+1		; dx = starting port number.
	mo User Data Area
;	  ah, si, di, bp are undefined.
; Exit:	  ax = return or XIOS error code
;	  bx = ax
;	  ds = SYSDAT segment
;	  es = User Data Area
;	  si, di, bp, dx, cx are undefined.

entry:
	push	ds			; save segment registers.
	push	es
	cld				; set auto-increment.
	push	bx			; save PC-DOS function code.
	mov	bx,cs			; get code segment.
	mov	ds,bx			; make data segment the same.
	mov	bl,al			; bx = function number.
	mov	bh,0
	shl	bx,1			; bx = 2 * bx.
	mov	si,bx			; get index to tabal = sysdat ticks/second.
	mov	tickct,al		; reset count to N ticks.

	; set second flag.
	mov	dx,secflg		; dx = code for second flag.
	mov	cx,flgset		; cx = code for flag set.
	call	supif			; set second flag.

	; decrement disk time-out counter once per second till it's zero.
	cmp	diskto,0		; is disk time-out counter 0?
	je	ticksf			; hop if so.
	dec	diskto			; else decrement counter.

	; set tick flag.
ticksf:	mov	dx,ticflg		; dx = code for tick flag.
	mov	cx,flgset		; cx = code for flag setinterrupt vector.
	mov	es:word ptr .020h,offset tick_int	; set offset.
	mov	es:word ptr .022h,cs			; set segment.

	; initialize hardware timer.
	mov	dx,timca0		; timer 0 max count a.
	mov	ax,timcnt		; ax = interval count.
	out	dx,ax			; set max count register.
	mov	dx,timmc0		; timer 0 mode/control word port.
	mov	ax,timbeg		; ax = code to begin timer 0.
	out	dx,ax			; start timer 0 running.

	; Allow timer interrupts to occur.
	mov	dx,inttcr		; dx = timer int. control reg.
	mov	ax,0003h		; av	cx,nsio			; cx = number of ports to init.
initsl:	mov	al,0aah			; force idle.
	out	dx,al
	call	fdelay			; wait a little.
	mov	al,040h			; reset.
	out	dx,al
	call	fdelay			; wait a little.
	mov	al,0ceh			; 8 stop bits.
	out	dx,al
	call	fdelay			; wait a little.
	mov	al,037h			; enable.
	out	dx,al
	call	fdelay			; wait a little.
	inc dx	! inc dx		; dx = next port address.
	loop	initsl			; loop until done.

	endif

	; Initialize screen buffers.
	mov	ax,cs			; es = cs.
	mov	es,ax
	cld				le.
	pop	bx			; restore PC-DOS function code.
	call	functab[si]		; call function through table.
	mov	bx,ax			; for return.
	pop	es			; restore segment registers.
	pop	ds
	retf

;
; SUPIF - Routine to allow XIOS to make calls to CCP/M XDOS.
; Entry:  cx = function #
;	  dx = parameter
;	  ds = parameter segment if address
;	  es = user data area
; Exit:	  bx = ax = return
;	  cx = error code for RTM functions
;	  es = return segment if address
;

supif:
	push	es		; save extra segment.
	m.
	call	supif			; set tick flag.

	; reset timer interrupt.
	mov	dx,inteoi		; dx = end-of-interrupt port.
	mov	ax,8000h		; ax = non-specific eoi code.
	out	dx,ax			; reset timer interrupt.

	; restore registers.
	pop es ! pop di
	pop si ! pop bp
	pop dx ! pop cx
	pop bx ! pop ax
	mov	ss,tickss
	mov	sp,ticksp
	pop	ds
	jmpf	cs:dword ptr .0038h	; to dispatcher.
	endif				; end of clock conditional.

	; IO_CISR - Console Input Interrupt Service Routine.

	if	conint			; if using console intex = clear mask bit, priority=3.
	out	dx,ax			; send to 80186.

	endif				; end tick conditional.

	if	conint			; if console interrupts.

	; initialize console interrupt vectors.
	mov	es:word ptr .080h,offset io_cisr	; vector 20h.
	mov	es:word ptr .082h,cs

	; initialize 8259 interrupt controller.
	mov	dx,inta0		; dx = control port a0 = 0.
	mov	al,19h			; al = ICW1.
	out	dx,al
	mov	dx,inta1		; dx = control port a0 = 1.
	mov	al,20h			; al = vector #20.
	out	dx,al
	mov	al,0			; al = slave #0.; direction = forward.

	if	vcsbuf			; if virtual console screen buffers.
	mov	cx,nvirt*maxcol*maxrow	; cx = number of words.
	mov	di,offset scbuf0	; di = starting address.
	mov	ax,0f20h		; ax = bright space.
	rep	stosw			; write ax to cx words.
	endif

	; Initialize cursor positions.
	mov	cx,nvirt		; cx = number of virtual consoles.
	mov	di,offset curpos	; di = start of cursor position table.
	mov	al,0			; al = column 0.
	mov	ah,23			; ah = row 23.
	rep	stosw			; write ax to cx words at di.
ov	bx,rlr
	mov	es,p_uda[bx]
	mov	ch,0
	callf	cs:dword ptr supervisor
	pop	es		; restore extra segment.
	ret

nmiint:	retf				; fill in later.


	; Timer Interrupt Handler.

tickss	dw	0			; user stack segment.
ticksp	dw	0			; user stack offset.
tickax	dw	0			; user ax register.
tickct	db	60			; tick count

tickint:
	if	clock			; if clock enabled.
	push	ds			; save current data segment.
	mov	ds,sysdat		; use xios data segment instead.
	mov	tickss,ss		; save user stack segment.
	mov	ticksrrupts.
coniss	dw	0			; user stack segment.
conisp	dw	0			; user stack offset.
coniax	dw	0			; user ax register.

io_cisr:
	; save registers.
	push	ds
	mov	ds,sysdat		; use xios data segment.
	mov	coniss,ss
	mov	conisp,sp
	mov	coniax,ax
	mov	ax,cs
	mov	ss,ax
	mov	sp,offset cistkb	; use stack in xios.
	push coniax! push bx! push cx! push dx
	push bp! push si! push di! push es
	mov bx,ds! mov es,bx		; es = ds.
	mov	ds,ax			; ds = cs.

	; poll console keyboards to determine which caused int
	out	dx,al
	mov	al,1			; al = 8086/8088 mode.
	out	dx,al

	mov	al,0feh			; al = enable v0.
	out	dx,al

	; initialize 80186 interrupt controller.
	mov	dx,intcr1		; dx = int1 control register port.
	mov	ax,0032h		; set cascade mode, priority=2.
	out	dx,al			; send to 80186 interrupt controller.

	; set 2681 console input interrupt mask bit.
	mov	dx,conimr		; dx = 2681 DUART int mask reg port.
	mov	al,2			; set bit 1 on.
	out	dx,al

	endif				; end console interupts.

	; initialize printer
	; Print sign-on message.
	mov	bx,(offset signon)
	call	prtmsg			; print signon.

	pushf				; ax = flags.
	pop	ax
	cli				; clear interrupt flag.
	mov	ss,int_ssreg		; restore stack for return.
	mov	sp,int_spreg
	push	ax			; flags = ax.
	popf

	mov	bx,rlr			; restore ES.
	mov	es,p_uda[bx]
	retf				; back to CCP/M's init.


; XIOS Entry Routine.
; Entry:  al = function number
;	  bx = PC-MODE parameter
;	  cx = first parameter
;	  dx = second parameter
;	  ds = SYSDAT segment
;	  es =p,sp		; save user stack offset.
	mov	tickax,ax		; save user ax register.
	mov	ax,cs			; ax = code segment.
	mov	ss,ax			; ss = code segment.
	mov	sp,offset ticktos	; use local stack.

	push	tickax! push bx		; save machine context on stack.
	push	cx ! push dx
	push	bp ! push si
	push	di ! push es

	mov	bx,ds			; es = sysdat page.
	mov	es,bx
	mov	ds,ax			; ds = cs.

	; check to set second flag.
	dec	tickct			; count down tick flag.
	jnz	ticksf			; not zero, continue.
	mov	al,es:ticks_sec		; er.
io_cicr:
	sub	bx,offset cnstbl+2	; bx = 4 * keyboard number.
	shr	bx,1			; bx = 2 * keyboard number.
	push	bx			; save 2 * keyboard number.
	mov	dx,cndtbl[bx]		; dx = data port.
	in	al,dx			; al = keyboard data.
	and	al,7fh			; strip most significant bit.
	shl	bx,1			; bx = 4 * keyboard number.
	shl	bx,1			; bx = 8 * keyboard number.
	add	bx,offset cibtab	; bx = console input table entry adr.
	mov	di,4[bx]		; di = position to put character.
	mov	[di],al			; put character into buffer.
	cmp	dd out top 4 bits.
	and	cl,0fh			; mask for top 4 bits only.
	and	ax,0fff0h
	add	dx,ax			; add shifted segment to offset.
	mov	al,0			; clear.
	adc	al,cl			; add top 4 & carry.
	mov	msb20,al		; save bits a16-a19.
	mov	lsb20,dx		; save bits a00-a15.
	ret


	; All undefined interrupt call come here.
	; It usually means a process has crashed.

int_trap:
	cli				; disable interrupts during service.
	mov	ax,cs
	mov	ds,ax			; get our data segment.
	mov	bx,(offset trpmsg)
	call	prtmsg			; print tdw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,1,nvirt0+1 ; res, mimic, source, physical, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt1 gt 2
	dw	offset ccb12,0	; virtual console link, reserved.

ccb12	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,1,nvirt0+2 ; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt1 gt 3
	dw	offset 
	if	ncrts gt 3
	; physical console 3.
nv02	equ	nv01+nvirt2	; number of virtuals on consoles 0-2.
ccb30	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,3,nv02	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt3 gt 1
	dw	offset ccb31,0	; virtual console link, reserved.

ccb31	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,3,nv02+1	; res, mimic, source, physical, virt.
	dw	0,2,10		; reserved, stati,2[bx]		; was that last buffer position?
	jne	io_ciin			; hop if not.
	mov	ax,[bx]			; ax = buffer addrecй if so.
	mov	4[bx],ax		; wrap around to buffer beginning.
	jmps	io_cini			; skip over increment.
io_ciin:
	inc	word ptr 4[bx]		; bump to next buffer position.
io_cini:

	; reset interrupt in 8259.
io_ciex:
	mov	al,60h			; issue non-specific eoi.
	mov	dx,inta0		; dx = 8259 a0=0 port number.
	out	dx,al			; do it.

	; reset interrupt in 80186.
	mov	dx,inteoi		; dx = end-of-interrupt port.
rap message.
	mov	cx,0
	int	224			; go to the system.


	; Console Control Blocks (CCB's).

	; physical console 0.
ccb0	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,0,0	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt0 gt 1
	dw	offset ccb01,0	; virtual console link, reserved.

ccb01	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,0,1	; res, mimic, source, physical, virt.
	dw	0,2,10		; reccb13,0	; virtual console link, reserved.

ccb13	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,1,nvirt0+3 ; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.
	endif

	if	ncrts gt 2
	; physical console 2.
nv01	equ	nvirt0+nvirt1	; number of virtuals on physical 0 and 1.
ccb20	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,2,nv01	; res, mimic, msource, phe flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt3 gt 2
	dw	offset ccb32,0	; virtual console link, reserved.

ccb32	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,3,nv02+2	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt3 gt 3
	dw	offset ccb33,0	; virtual console link, reserved.

ccb33	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,3,nv02+3	; res, mimic, msource, phys, v
	mov	ax,8000h		; ax = non-specific eoi code.
	out	dx,ax			; reset interrupt.

	pop	dx			; dx = 2 * keyboard number.

	; see if there's a process waiting for a keyboard character.
	shr	dx,1			; dx = keybord number.
	mov	bx,dx			; bx = keyboard number.
	cmp	byte ptr ciftab[bx],0	; is a process waiting?
	je	io_cirt			; return if not.

	; set flag in ccpm.
	mov	byte ptr ciftab[bx],0	; clear process waiting flag.
	add	dl,4			; first 4 are reserved.
	mov	cx,flgset		; cx = code for flag set.
	call	served, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt0 gt 2
	dw	offset ccb02,0	; virtual console link, reserved.

ccb02	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,0,2	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt0 gt 3
	dw	offset ccb03,0	; virtual console link, reserved.

ccb03	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,0,3	; res, mimic, msource, phys,ysical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt2 gt 1
	dw	offset ccb21,0	; virtual console link, reserved.

ccb21	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,2,nv01+1	; res, mimic, source, physical, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt2 gt 2
	dw	offset ccb22,0	; virtual console link, reserved.

ccb22	dw	0,0,0		; owner, reserved.
	irt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.

	endif

	if	ncrts gt 4
	; physical console 4.
nv03	equ	nv02+nvirt3	; number of virtuals on consoles 0-3.
ccb40	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,4,nv03	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt4 gtsupif			; set console flag.

	; restore registers.
io_cirt:
	pop es! pop di! pop si! pop bp
	pop dx! pop cx! pop bx! pop ax
	mov	ss,coniss
	mov	sp,conisp
	pop	ds
	iret				; return from interrupt.
	endif				; end of conint conditional.


	; Compute physical dma address from segment and offset.
	; Inputs:  ax = segment, dx = offset.
	; Outputs:  msb20 = most signifcant bits, lsb20 = least sig.

comdma:	mov	cl,4			; shift count.
	rol	ax,cl			; shift segment left 4.
	mov	cl,al			; save shifte virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.

	if	ncrts gt 1
	; physical console 1.
ccb10	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,1,nvirt0	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt1 gt 1
	dw	offset ccb11,0	; virtual console link, reserved.

ccb11	db	0,0,0ffh,0ffh,2,nv01+2	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt2 gt 3
	dw	offset ccb23,0	; virtual console link, reserved.

ccb23	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,2,nv01+3	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.
	endif
rved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt4 gt 3
	dw	offset ccb43,0	; virtual console link, reserved.

ccb43	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,4,nv03+3	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.

	endif

	if	ncrts gt 5
	; physical console 5.
nv04	equ	nv03+nvirt4	; number of virtuals on consoles 0-4.
ccb50	dw	0,0,0		; owner, resermic, source, physical, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt6 gt 2
	dw	offset ccb62,0	; virtual console link, reserved.

ccb62	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,6,nv05+2	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt6 gt 3
	dw	offset ccb63,0	; virtual console link, reserved.

ccb63	dw	0,0,0		; owner.
ified
	; serial I/O device.
	; Entry:  al=0, dl=serial i/o device number.
	; Exit:  al=0 if no character ready.
	;        al=0ffh if character ready.
	;        bl=al.

io_const:
	mov	dh,0		; clear upper dx.
	shl	dx,1		; device number by 4.
	shl	dx,1
	mov	bx,dx		; put into index register.
	add	bx,offset cnstbl	; address of port number.
	mov	dx,[bx]		; get port number.
	in	al,dx		; read status port.
	add	bx,2		; point at mask.
	mov	ah,[bx]		; get input ready mask.
	and	al,ah		; test for readydl right 5 bits = number within category.
	; Exit:  dl right 5 bits = number within category.
	;	 z flag set if time-out error.
	; Preserve:  ax, cx, 5 least significant bits of dx.

wait:
	if	conint		; if console interrupts.
	test	dl,11100000b	; is it a console input?
	jnz	waitpol		; handle with poll if not.

	; Must be console input.  See if there's a character ready.
	push	ax		; save registers.
	push	cx
	push	dx
	mov	bx,dx		; bx = keyboard number.
	mov	cl,3		; cl = number of shifts.
	shl	ved.
	db	0,0,0ffh,0ffh,5,nv04	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt5 gt 1
	dw	offset ccb51,0	; virtual console link, reserved.

ccb51	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,5,nv04+1	; res, mimic, source, physical, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt5 gt 2
	dw	offset ccb52,0	; virtual console 
	db	0,0,0ffh,0ffh,6,nv05+3	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.

	endif

	if	ncrts gt 7
	; physical console 7.
nv06	equ	nv05+nvirt6	; number of virtuals on consoles 0-6.
ccb70	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,7,nv06	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0.
	jz	cs_ext		; result zero, exit test (00=not ready).
	or	al,0ffh		; not zero, set al (ff=ready).
	mov	bl,al		; for return.
	ret			; return from console status (flag in al).

	; Console output status check.
	; Return the output status of the specified
	; serial I/O device.
	; Entry:  al=0, dl=serial i/o device number.
	; Exit:  al=0 if no character ready.
	;        al=0ffh if character ready.
	;        bl=al.

io_pollco:
	mov	dh,0		; clear upper dx.
	shl	dx,1		; device number by 4.
	shl	dxbx,cl		; bx = 8 * keyboard number.
	add	bx,offset cibtab	; bx = adr of keyboard entry.
	mov	cx,4[bx]	; cx = address to put character.
	cmp	6[bx],cx	; is it same as address to get char?
	jne	waitxt		; no need to wait if not.

	; Wait for interrupt if no characters are ready.
	mov	bx,dx		; bx = keyboard number.
	mov	ciftab[bx],1	; set process waiting flag.
	add	dl,4		; flags 0-3 are reserved.
	mov	cl,84h		; code for dev_waitflag.
	call	supif		; set wait flag, wait for interrupt.
	jmps	waitxt		; relink, reserved.

ccb52	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,5,nv04+2	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt5 gt 3
	dw	offset ccb53,0	; virtual console link, reserved.

ccb53	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,5,nv04+3	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	end,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt7 gt 1
	dw	offset ccb71,0	; virtual console link, reserved.

ccb71	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,7,nv06+1	; res, mimic, source, physical, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt7 gt 2
	dw	offset ccb72,0	; virtual console link, reserved.

ccb72	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,7,nv06+2	; res, mimic, msource, phys, virt.
	dw	0,2,10		; ,1
	mov	bx,dx		; put into index register.
	add	bx,offset cnstbl	; address of port number.
	mov	dx,[bx]		; get port number.
	in	al,dx		; read status port.
	add	bx,3		; point at mask.
	mov	ah,[bx]		; get output ready mask.
	and	al,ah		; look only at ready bit(s).
	xor	al,ah		; compare the bit(s).
	jnz	io_cnrd		; if not same, exit not ready.

	if	dtrcon		; if dtr handshaking for console.
	cmp	dh,0		; is it a Duplex port?
	jz	io_crdy		; ready if not.
	mov	dx,coninp	; else dx = input port address.
store registers and return.
waitpol:
	endif

	if	not debugp	; if not debugging.
	push	ax		; save operation code.
	push	cx		; save possible character.
	push	dx		; save device number.
	mov	al,13		; make it look like outside call.
	call	io_poll		; see if device is ready.
	cmp	al,0ffh		; is device ready?
	je	waitxt		; exit if so.
	mov	cl,83h		; get dev_poll code for xdos.
	pop	dx		; recover device # for dev_poll.
	push	dx		; save it back for i/o routines.
	call	supif		; do dev_poll.
	jmps	waitxtif
	dw	0,0		; virtual console link, reserved.

	endif

	if	ncrts gt 6
	; physical console 6.
nv05	equ	nv04+nvirt5	; number of virtuals on consoles 0-5.
ccb60	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,6,nv05	; res, mimic, msource, physical, virt.
	dw	0,0,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt6 gt 1
	dw	offset ccb61,0	; virtual console link, reserved.

ccb61	dw	0,0,0		; owner, reserved.
	db	0,0,0ffh,0ffh,6,nv05+1	; res, mireserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	if	nvirt7 gt 3
	dw	offset ccb73,0	; virtual console link, reserved.

ccb73	dw	0,0,0		; owner.
	db	0,0,0ffh,0ffh,7,nv06+3	; res, mimic, msource, phys, virt.
	dw	0,2,10		; reserved, state flags, max buffer.
	dw	0,0,0,0,0,0	; reserved.
	dw	0,0,0,0,0	; reserved.
	endif
	endif
	endif
	dw	0,0		; virtual console link, reserved.

	endif


	; Console input status check.
	; Return the input status of the spec
	in	al,dx		; al = dsr bits from input port.
	test	al,condsr	; look at console dsr bit.
	jnz	io_cnrd		; hop if not ready.
	endif
io_crdy:
	mov	al,0ffh		; exit with ready condition.
	jmps	cs_ext		; exit.
io_cnrd:
	mov	al,0		; not ready exit.
cs_ext:
	mov	bl,al		; for return.
	ret			; return from console status (flag in al).

	; Wait for i/o device to become ready.
	; Relinquish control to xdos until ready.
	; Entry:  dl = device number.
	;	dl left  3 bits = device category. (see polltbl)
	;	

waitxt:	pop	dx		; restore registers.
	and	dx,001fh	; clear device category bits.
	pop	cx
	pop	ax
	cmp	ercode,80h	; is there a disk time-out error?
	ret

	; Check status device whose number is in dl.
	; Device numbers are assigned thusly:
	;	left 3 bits = device category
	;	right 5 bits = number within category

io_poll:
	mov	bh,0		; bx = device number.
	mov	bl,dl
	and	dl,1fh		; clear category bits.
	mov	cl,4		; divide by 16.
	shr	bx,cl
	and	bx,0fffeh	; clear bit 0.
	jmp	polltbl[bx]	; rio_csw		; switch if so.
	inc	bl		; set code for 1.
	cmp	al,vkey1	; virtual key 1?
	jz	io_csw		; switch if so.
	inc	bl		; set code for 2.
	cmp	al,vkey2	; virtual key 2?
	jz	io_csw		; switch if so.
	inc	bl		; set code for 3.
	cmp	al,vkey3	; virtual key 3?
	jz	io_csw		; switch if so.
	ret
io_csw:
	mov	ax,bx		; use bx that has switch codes.
	ret

	; must be in pc mode, so return scan code in ah.
io_nosw:
	mov	bx,ax		; bx = ke9board character.
	mov	ah,ksctbl[bx]	; ah = scan code from table.
	t36 6
	db	8		; 37 7
	db	9		; 38 8
	db	10		; 39 9
	db	39	OR 80h	; 3A :
	db	39		; 3B ;
	db	51	OR 80h	; 3C <
	db	13	OR 80h	; 3D =
	db	52	OR 80h	; 3E >
	db	53	OR 80h	; 3F ?
	db	3	OR 80h	; 40 @
	db	30	OR 80h	; 41 A
	db	48	OR 80h	; 42 B
	db	46	OR 80h	; 43 C
	db	32	OR 80h	; 44 D
	db	18	OR 80h	; 45 E
	db	33	OR 80h	; 46 F
	db	34	OR 80h	; 47 G
	db	35	OR 80h	; 48 H
	db	23	OR 80h	; 49 I
	db	36	OR 80h	; 4A J
	db	37	OR 80h	; 4B K
	db	38	OR 80h	; 4C L
	db	39	OR 80h	; 4D M
	db	49	OR 80h	; 4E N
	db	2
	mov	dx,curpos[di]	; get cursor position.
	cmp	al,lf		; line feed?
	je	io_colf		; hop if so.
	dec	dl		; col = col-1, possible bs.
	cmp	al,bs		; back space?
	je	io_cocp		; hop if so.
	mov	dl,0		; column = 0 for possible cr.
	cmp	al,cr		; is it a carriage-return?
	je	io_cosp2
	cmp	al,20h		; is it some other control character?
	jc	io_coex		; exit if so.

	; write character and attribute byte into screen buffer.
	call	io_vsad		; bx = address in buffer.

	if	vcsbuf		; if virtual console screen buest is in status routine.


	; console input.
	; Return a character from the console keyboard or
	; a serial I/O device.
	; Entry:  al = 1, dl = serial i/o device number.
	; Exit:  ah = 0 if returning data, 0ffh if switch.
	;	 ah = scan code if in pc mode.
	;        al = character or virtual console number.

io_conin:
	call	wait		; wait until device is ready.

	if	conint		; if console interrupts.
	; read keyboard character from console input buffer.
	mov	dh,0		; dx = console number.
	mov	bxest	ah,80h		; would shift be down on pc?
	jz	io_noex		; normal exit if not.
	mov	bh,1		; set shift flag.
	and	ah,7fh		; remove shift bit
io_noex:
	mov	shflg,bh	; store shift flag.
	ret			; return from console input (char in al).

	; Scan code table for PC-DOS software.
	; Position is input ascii code, 0-7fh.
	; Lower 7 bits of entry is pc-mode scan code.
	; Most significant bit is set to indicate shift.

;	    scan code	shift	 hex ascii
;	    ---------   -----    ---------
ksctbl	db	0		; 00 n4	OR 80h	; 4F O
	db	25	OR 80h	; 50 P
	db	16	OR 80h	; 51 Q
	db	19	OR 80h	; 52 R
	db	31	OR 80h	; 53 S
	db	20	OR 80h	; 54 T
	db	22	OR 80h	; 55 U
	db	47	OR 80h	; 56 V
	db	17	OR 80h	; 57 W
	db	45	OR 80h	; 58 X
	db	21	OR 80h	; 59 Y
	db	44	OR 80h	; 5A Z
	db	26		; 5B [
	db	54		; 5C \
	db	27		; 5D ]
	db	7	OR 80h	; 5E ^
	db	12	OR 80h	; 5F _
	db	41		; 60 `
	db	30		; 61 a
	db	48		; 62 b
	db	46		; 63 c
	db	32		; 64 d
	db	18		; 65 e
	db	33		; 66 f
	db	34		; 67 g
	db	35		; 68 h
	db	23		; 69 i
	dffer.
	mov	[bx],al		; put character into buffer.
	endif

	; Increment curpos (cursor position).
io_incp:
	mov	dx,curpos[di]		; dh = row, dl = column.
	inc	dl			; increment column.
	cmp	dl,nocols		; is it past end of line?
	jc	io_cocp			; exit if not.
	mov	dl,0			; start at left again.
io_colf:
	inc	dh			; down to next row.
	cmp	dh,norows		; is it past end of screen?
	jc	io_cocp			; exit if not.
	mov	dh,norows		; set to last row.
	dec	dh
	call	io_vbup			; scroll buffer up.

	; Check limits,dx		; bx = console number.
	mov	cl,3		; cl = 3 for multiply by 8.
	shl	bx,cl		; bx = 8 * console number.
	add	bx,offset cibtab	; bx = cons. input buf entry adr.
	mov	si,6[bx]		; si = next position to get char.
	mov	al,[si]			; al = character from buffer.
	cmp	si,2[bx]		; is pointer at last position?
	jne	io_conn			; hop if not.
	mov	cx,[bx]			; cx = buffer address if so.
	mov	6[bx],cx		; reset pointer to begining.
	jmps	io_conm			; skip the increment.
io_conn:
	inc	word ptr 6[bx]		; increment bull
	db	0		; 01 soh
	db	0		; 02 stx
	db	0		; 03 etx
	db	0		; 04 eot
	db	0		; 05 enq
	db	0		; 06 ack
	db	0		; 07 bel
	db	14		; 08 bs  backspace
	db	15		; 09 ht  tab
	db	80		; 0A lf  cursor down
	db	72		; 0B vt  cursor up
	db	77		; 0C ff  cursor right
	db	28		; 0D cr  return
	db	0		; 0E so
	db	0		; 0F si
	db	0		; 10 dle
	db	0		; 11 dc1
	db	0		; 12 dc2
	db	0		; 13 dc3
	db	0		; 14 dc4
	db	0		; 15 nak
	db	80		; 16 syn cursor down
	db	0		; 17 etb
	db	0		; 18 can
	db	0		; 19 em
	db	0		; 1b	36		; 6A j
	db	37		; 6B k
	db	38		; 6C l
	db	39		; 6D m
	db	49		; 6E n
	db	24		; 6F o
	db	25		; 70 p
	db	16		; 71 q
	db	19		; 72 r
	db	31		; 73 s
	db	20		; 74 t
	db	22		; 75 u
	db	47		; 76 v
	db	17		; 77 w
	db	45		; 78 x
	db	21		; 79 y
	db	44		; 7A z
	db	26	OR 80h	; 7B {
	db	54	OR 80h	; 7C |
	db	27	OR 80h	; 7D }
	db	41	OR 80h	; 7E ~
	db	83		; 7F del


	; console output.
	; Display and/or output a character to the specified
	; serial i/o device.  Also put character into screen
	; on row (dl) and column (dh) then
	; set cursor = dx.
io_cocp:
	test	dl,80h			; is column negative?
	jz	io_cosp1			; hop if not.
	mov	dl,0			; else set column = 0.
io_cosp1:
	cmp	dl,nocols		; is column => no of columns?
	jc	io_cosp2			; hop if not.
	mov	dl,nocols		; else get last column number.
	dec	dl
io_cosp2:
	test	dh,80h			; is row negative?
	jz	io_cosp3			; hop if not.
	mov	dh,0			; else set row = 0.
io_cosp3:
	cmp	dh,norows		; is row => no of rows?
	jc	io_cosp			; hop if not.
	mov	dhuffer pointer.
io_conm:
	endif

	if	not conint	; if not console interrupts.
	shl	dx,1		; multiply by 2 for table.
	mov	di,dx		; put into index register.
	mov	dx,cndtbl[di]	; get console data port adr.
	in	al,dx		; read console data.
	endif

	and	al,7fh		; strip parity.
	mov	ah,0		; code for no virtual switch.
	cmp	pcflag,1	; is it in pc mode?
	je	io_nosw		; ignore virtual keys if so.

	mov	bh,0ffh		; code for virtual switch.
	mov	bl,0		; set code for 0.
	cmp	al,vkey0	; virtual key 0?
	jz	A sub
	db	1		; 1B esc escape
	db	0		; 1C fs
	db	0		; 1D gs
	db	71		; 1E rs  home
	db	0		; 1F us
	db	0		; 20 sp
	db	2	OR 80h	; 21 !
	db	40	OR 80h	; 22 "
	db	4	OR 80h	; 23 #
	db	5	OR 80h	; 24 $
	db	6	OR 80h	; 25 %
	db	8	OR 80h	; 26 &
	db	40		; 27 '
	db	10	OR 80h	; 28 (
	db	11	OR 80h	; 29 )
	db	9	OR 80h	; 2A *
	db	13	OR 80h	; 2B +
	db	51		; 2C ,
	db	12		; 2D -
	db	52		; 2E .
	db	53		; 2F /
	db	11		; 30 0
	db	2		; 31 1
	db	3		; 32 2
	db	4		; 33 3
	db	5		; 34 4
	db	6		; 35 5
	db	7		;  buffer in the right place.
	; Entry:  al = 2, cl = character, dl = virtual console.
	; Exit: whatever.

io_conout:
	push	dx		; save virtual console number.
	call	divirt		; di = virt cons * 2, dl = physical.
	pop	ax		; al = virtual console number.
	mov	bx,dx		; bx = physical console number.
	cmp	forgnd[bx],al	; is this virtual in foreground?
	jne	io_conc		; hop if not.
	call	io_conu		; write character to console.
io_conc:
	mov	al,cl		; al = character.

	; check for screen control characters.
egory = 1.
	call	wait		; wait until it's ready.
	shl	dx,1		; multiply by 2 for table.
	mov	di,dx		; put into index register.
	mov	dx,cndtbl[di]	; get port address.
	mov	al,cl		; get character from cl.
	out	dx,al		; send character to console.
	pop	di		; restore virtual console number * 2.
	ret


	; Print character in cl, saving main registers.
	; This is used as a utility print routine for
	; messages.  It's also currently called from the
	; video routines.

conout:
	push	ax		; save registerat bx.
	mov	si,bx		; si = starting string address.
io_swl3:
	mov	ax,[si]		; ax = attribute, character.
	add	si,2		; point si at next character.
	call	io_vonu		; print character.
	loop	io_swl3		; dec cx, loop until cx = 0.
io_swno:
	mov	cl,nocols	; cx = number of columns.
	mov	ch,0
	shl	cx,1		; cx = number of bytes.
	add	bx,cx		; bx = address of next row.
	shr	cx,1		; cx = number of words.
	dec	dh		; decrement row counter.
	jnz	io_swl1		; repeat if not zero.
	endif

	ret


	; Display statindex register.
	add	bx,offset lpstbl	; address of port number.
	mov	dx,[bx]		; get status port number.
	in	al,dx		; read printer status.
	add	bx,3		; point to status mask.
	mov	ah,[bx]		; get status mask.
	and	al,ah		; look at important bit(s).
	xor	al,ah		; compare status bits.
	jnz	io_lnrd		; if not same, exit not ready.
	cmp	dh,0		; is it a Duplex port?
	jz	io_lrdy		; ready if not.
	mov	dx,lptinp	; get input port address.
	in	al,dx		; read input port.
	test	al,lptdsr	; look at dsr bit.
	jn

io_pollao:
	mov	dx,auxost	; get aux output status port.
	in	al,dx		; read aux output status.
	and	al,auxomk	; is aux output ready?
	jz	io_auxe		; exit with al = 00 if not.
	or	al,0ffh		; exit with al = ff if so.
	jmps	io_auxe		; rest is above.


	; *********************************************************
	; ************ subroutine to print messages ***************
	; *********************************************************

prtmsg:
	mov	cl,[bx]		; get next character from string.
	test	cs.
	push	bx
	push	cx
	push	dx
	mov	dl,0		; console 0,
	call	io_conout	; print character.
	pop	dx		; restore registers.
	pop	cx
	pop	bx
	pop	ax
	ret

	; IO_SWITCH - Switch Screen.
	; Place the current virtual console into the background
	; and the specified virtual console into the foreground.
	; Entry:  al = 7, dl = virtual console # to switch to.
	; Exit:  set foreground table.

io_switch:
	if	vcsbuf		; if virtual console screen buffer.
	push	dx		; save virtual console number.
	call	dius line.
	; Display specified text on the status line.
	; Entry:  al = 8, if cx = 0, continue to update the normal
	;	status line.  If cx = offset, print string at dx:cx.
	;	If cx = 0ffffh, resume normal status line display.
	;	dl = physical console to display status line on.
	;	dx = segment address of optional string (cx<>0).
	; Exit values: none.

io_statline:
	; not implemented.
	ret


	; List control blocks.

lcb0	dw	0		; owner.
	dw	0,0,0		; reserved.
	db	0,0ffh		; reserved, m-source.
z	io_lnrd		; hop if not ready.
io_lrdy:
	mov	al,0ffh		; set ready flag.
	jmps	ps_ext		; exit.
io_lnrd:
	mov	al,0		; set not ready flag.
ps_ext:
	mov	bl,al		; bl = al for exit.
	ret			; return from printer status (flag in al).

	; List output.
	; Output character to specified list device.
	; Entry:  al = 4, cl = character, dl = list device number.
	; Exit value: none.

io_list:
	or	dl,2 shl 5	; set device category = 2.
	call	wait		; wait until device is ready.
	mov	dh,0		; set dx = device nl,cl		; check if zero.
	jz	prtex		; if zero branch to return.
	call	conout		; print character at console.
	inc	bx		; point to next character.
	jmps	prtmsg		; loop till string terminator found.
prtex:
	ret			; exit from print routine.


	; *********************************************************
	; ************ PC-MODE Character I/O Routines *************
	; *********************************************************

	; XIOS BACK DOOR ENTRY (whatever that means)

xios_v1_entry:
	mov	bx,offsetvirt		; dl = physical, di = virtual*2.
	mov	bx,dx		; bx = physical console number.
	pop	ax		; al = virtual console number.
	mov	forgnd[bx],al	; set foreground for this physical console.
	mov	bx,scbuft[di]	; bx = screen buffer address.
	mov	dh,norows	; dh = number of rows.
	mov	cl,nocols	; cl = number of columns.
	mov	ch,0		; cx = number of columns.
io_swl1:
	mov	si,bx		; si --> first character in row.
	shl	cx,1		; cx = number of bytes.
	add	si,cx		; si --> last character in row+1.
	shr	cx,1		; c
	if	nptrs gt 1
lcb1	dw	0		; owner.
	dw	0,0,0		; reserved.
	db	0,0ffh		; reserved, m-source.
	endif
	if	nptrs gt 2
lcb2	dw	0		; owner.
	dw	0,0,0		; reserved.
	dw	0,0ffh		; reserved, m-source.
	endif
	if	nptrs gt 3
lcb3	dw	0		; owner.
	dw	0,0,0		; reserved.
	dw	0,0ffh		; reserved, m-source.
	endif
	if	nptrs gt 4
lcb4	dw	0		; owner.
	dw	0,0,0		; reserved.
	dw	0,0ffh		; reserved, m-source.
	endif
	if	nptrs gt 5
lcb5	dw	0		; owner.
	dw	0,0,0		; reserved.
	dw	0,0ffh		; reserved m-source.
umber.
	shl	dx,1		; multiply by 2 for table.
	mov	di,dx		; put into index register.
	mov	dx,lpdtbl[di]	; get printer data port address.
	mov	al,cl		; get character from cl.
	out	dx,al		; print character.
	ret			; return from printer output.

	; Auxilliary Input Driver.

io_auxin:
	or	dl,3 shl 5	; set category = 3.
	call	wait		; wait until device is ready.
	mov	dx,auxin	; get port address.
	in	al,dx		; read the incoming byte.
	ret

	; Auxilliary Output Driver.

io_auxout:
	or	dl,4 shl 5	; e6msg		; print "INT E6"
	call	prtmsg
	iret

	; WW_KEY	Read a window.
	; Back door entry to pass window manager a key stroke.
	; Entry:
	;	cl = 0ffh => input/status
	;		exit:	al = char if char ready
	;			al = 0 if no char ready
	;	cl = 0feh => status only
	;		exit:	al = 0ffh if char ready
	;			al = 0 if no char ready
	;	cl < 0feh => wait for input
	;		exit:	al = char when ready
	; Exit:
	;	if al = char then
	;		ah = key type
	;			0 means regular
	;			0ffh means special

ww_key:
	mov	dlx = number of words.
	inc	cx		; cx = number of words + 1.
io_swl2:
	sub	si,2		; point si at previous character.
	mov	ax,[si]		; ax = character and attribute.
	cmp	al,' '		; is character a space?
	loope	io_swl2		; dec cx, loop while equal to space.

	; print carriage-return and line-feed.
	mov	al,cr		; al = carriage-return.
	call	io_vonu		; print it.
	mov	al,lf		; print line-feed.
	call	io_vonu
	cmp	cx,0		; are there any characters to print?
	je	io_swno		; hop if not.

	; print cx characters 	endif
	if	nptrs gt 6
lcb6	dw	0		; owner.
	dw	0,0,0		; reserved.
	dw	0,0ffh		; reserved m-source.
	endif
	if	nptrs gt 7
lcb7	dw	0		; owner.
	dw	0,0,0		; reserved.
	dw	0,0ffh		; reserved m-source.
	endif


	; List status.
	; Return list output status.
	; Entry:  al = 3, dl = list device number.
	; Exit:  al = 0ffh if device ready,
	;	 al = 0 if device not ready.
	;	 bl = al.

io_listst:
	mov	dh,0		; make dx = device number.
	shl	dx,1		; multiply by 4.
	shl	dx,1
	mov	bx,dx		; put into  set category = 4.
	call	wait		; wait until device is ready.
	mov	dx,auxout	; get port address.
	mov	al,cl		; get byte.
	out	dx,al		; send byte out.
	ret


	; Poll Auxilliary Device Input Status.

io_pollai:
	mov	dx,auxist	; get aux input status port.
	in	al,dx		; read aux input status.
	and	al,auximk	; is aux input ready?
	jz	io_auxe		; exit with al = 00 if not.
	or	al,0ffh		; exit with al = ff if so.
io_auxe:
	mov	bl,al		; make the same.
	ret


	; Poll Auxilliary Device Output Status.only.
ww_keyso:
	jmp	io_const	; read console status.


	; IO_SCREEN	GET/SET SCREEN
	; Get or set the current screen.
	; Entry:
	;	al = 1eh (30)
	;	ch = 0 for set, 1 for get
	;	cl = mode if ch = 0 (set)
	;	dl = virtual console number
	; Exit:
	;	ax = mode if ch = 1 (get)
	;	ax = 0ffffh if mode not supported (set)
	;	ax = 0fffeh if bad parameters (set)
	;	ax = 00000h if successful (set)
	;	es, ds, ss, sp preserved.

io_screen:
	cmp	ch,0			; is it a set?
	je	io_scs			; hop if so.

	; musrpos[di]		; new position same as old one?
	je	io_vrcpx		; exit if so.
	mov	dx,cx			; dx = cursor position.
	call	io_cocp			; check limits, set curpos.
	mov	bx,offset setcur	; get set cursor sequence adr.
	jmp	io_vseq			; do video sequence.

	; read cursor position.
io_vrcp:
	call	divirt			; di = virtual console number * 2.
	mov	ax,curpos[di]		; get cursor position.
io_vrcpx:
	ret

	; DIVIRT
	; Entry:  dl = virtual console number.
	; Exit:   dl = physical console number.
	;	  dh = 0.
	;	  dul			; loop back if not zero.
	endif

	ret

	; Clear screen.
	; Called by io_vsup and io_vsdn.
	; Entry:  bx = cursor address to start clear.
io_vcls:
	if	vcsbuf			; if virtual console screen buffer.
	push	bx			; save starting cursor position.
	mov	bx,offset clreos	; bx = clear screen sequence adr.
	call	io_vseq			; send sequence to CRT.
	pop	bx			; bx = starting cursor position.
	call	io_vsab			; bx = starting address.
	mov	ah,vidatr		; ah = video attribute.
	mov	al,20h			; ax = attribute/s restore address in buffer.
	push	bx			; save it back.
	call	io_vbdd			; insert line in screen buffer.
	pop	bx			; restore di.
	pop	dx			; restore count and console no.
	dec	dh			; decrement line counter.
	jnz	io_vsdl			; loop back if not zero.
	endif

	ret

	; read attribute/character.
io_vrat:
	call	divirt			; di = virtual console number * 2.
	call	io_vsad			; bx = address in screen buffer.
	mov	ax,[bx]			; get attribute and character.
	ret

	; write attribute/character.
io_vwat:
	callt be get screen.
	mov	ch,nocols		; get number of columns.
	mov	cl,scmode		; get screen mode.
	mov	ax,cx			; not clear which one.
	ret

	; must be set screen.
io_scs:	mov	scmode,cl		; set screen mode.
	mov	ax,0			; show successful set.
	ret

	; IO_VIDEO	VIDEO INPUT/OUTPUT
	; Manipulate the video screen.
	; Entry:
	;	al = 1fh (31)
	;	bl = subfunction
	;	cx = input parameter
	;	dx = input parameter
	; Exit:
	;	depends upon subfunction.
	;	es, ds, ss, sp preserved.

io_video:
	cmp	bl,15		i = virtual console number times 2.

divirt:	mov	dh,0			; dx = virtual console number.
	mov	di,dx			; di = virtual console number.
	mov	dl,vpcont[di]		; dl = physical console number.
	shl	di,1			; di = virtual console number * 2.
	ret

	; scroll up.
io_vsup:
	if	vcsbuf			; if virtual console screen buffer.
	call	io_vgp			; es = parameter segemnt, si = ofs.
	call	divirt			; di = virtual console number * 2.
	mov	ah,es:3[si]		; ah = attribute of blank line(s).
	call	io_vatr			; set attribute if cpace.
	mov	cx,cs			; get current segment.
	mov	es,cx			; segment to send the blanks.
	mov	cx,nochrs		; cx = no of words in buffer.
	shl	cx,1			; cx = no of bytes in buffer.
	add	cx,scbuft[di]		; cx = 1 byte past end of buffer.
	mov	di,bx			; di = starting address.
	sub	cx,di			; cx = no of bytes to clear.
	shr	cx,1			; cx = number of words to clear.
	cld				; increment di.
	rep	stosw			; write bright blanks into buffer.
	endif

	ret

	; scroll down.
io_vsdn:
	if	vcsbuf			; if virtual consol	io_vgp			; get parameter segment, offset.
	call	divirt			; di = virtual console number * 2.
	call	io_vsad			; bx = address in screen buffer.
	mov	al,es:0[si]		; get character in al.
	mov	ah,es:2[si]		; get attribute in ah.
	call	io_vatr			; test and send attribute.
	mov	cx,es:4[si]		; get character repeat count.
	jmps	io_vwatb		; hop around increment for now.
io_vwatl:
	call	io_incp			; increment cursor position.
io_vwatb:
	if	vcsbuf			; if virtual console screen buffer.
	mov	[bx],ax			; write 	; is it greater than 14?
	jc	io_vide			; hop if not.
	jmp	io_ret			; print error message if so.
io_vide:
	mov	bh,0			; bx = sub function number.
	shl	bx,1			; it's a word table.
	jmp	subtab[bx]		; jump to the routine.

	; Table of video subfunction addresses.
subtab	dw	io_ret			;  0: set mode not implemented.
	dw	io_ret			;  1: set cursor type not imp.
	dw	io_vscp			;  2: set cursor position.
	dw	io_vrcp			;  3: read cursor position.
	dw	io_ret			;  4: read light pen not imp.
	dw	io_ret			;  hanged.
	mov	dh,es:0[si]		; dh = number of lines to scroll.
	mov	bx,es:4[si]		; bx = upper left of window.
	mov	bl,0			; bl = left column for now.
	push	bx			; save starting cursor position.
	push	dx			; save number of lines to scroll.
	mov	cx,bx			; cx = starting cursor position.
	mov	bx,offset setcur	; bx = set cursor sequence adr.
	call	io_vseq			; set cursor on physical CRT.
	pop	dx			; dx = number of lines to scrolм.
	pop	bx			; restore starting cursor pos.
	cmp	dh,0			; if zero lines to scre screen buffer.
	call	io_vgp			; es = parameter segemnt, si = ofs.
	call	divirt			; di = virtual console number * 2.
	mov	ah,es:3[si]		; ah = attribute of blank line(s).
	call	io_vatr			; set attribute if changed.
	mov	dh,es:0[si]		; dh = number of lines to scroll.
	mov	bx,es:4[si]		; bx = upper left of window.
	mov	bl,0			; bl = left column for now.
	push	bx			; save starting cursor position.
	push	dx			; save number of lines to scroll.
	mov	cx,bx			; cx = starting cursor position.
	mov	bx,offsattribute and char.
	endif

	add	bx,2			; increment screen buffer ptr.
	call	io_vonc			; send cяaracter to screen.
	loop	io_vwatl		; loop until all chars sent.
	ret

	; write character.
io_vwc:
	call	io_vgp			; get parameter segment, offset.
	call	divirt			; di = virtual console number * 2.
	call	io_vsad			; bx = address in screen buffer.
	mov	al,es:0[si]		; al = character to write.
	mov	cx,es:4[si]		; cx = number of chars to write.
	jmps	io_vwcb			; no increment on first time.
io_vwcl:
	ca5: select display not imp.
	dw	io_vsup			;  6: scroll up.
	dw	io_vsdn			;  7: scroll down.
	dw	io_vrat			;  8: read attribute/character.
	dw	io_vwat			;  9: write attribute/character.
	dw	io_vwc			; 10: write character.
	dw	io_vgni			; 11: set color palette not imp.
	dw	io_vgni			; 12: write dot not implemented.
	dw	io_vgni			; 13: read dot not implemented.
	dw	io_vwsc			; 14: write serial character.

	; set cursor position.
io_vscp:
	call	divirt			; di = virtual console number * 2.
	cmp	cx,cuoll,
	je	io_vcls			;   clear the screen.
	call	io_vsab			; bx = address to delete lines.
io_vsul:
	push	dx			; save count and console no.
	push	bx			; save address in screen buffer.
	mov	bx,offset dellin	; bx = adr of delete line seq.
	call	io_vseq			; do it.
	pop	bx			; restore address in screen buf.
	push	bx			; save it back.
	call	io_vbud			; delete line in screen buffer.
	pop	bx			; restore adr in buf.
	pop	dx			; restore count and console no.
	dec	dh			; decrement line counter.
	jnz	io_vset setcur	; bx = set cursor sequence adr.
	call	io_vseq			; set cursor on physical CRT.
	pop	dx			; dx = number of lines to scroll.
	pop	bx			; restore starting cursor pos.
	cmp	dh,0			; if zero lines to scroll,
	je	io_vcls			;   clear the screen.
	call	io_vsab			; bx = address to insert lines.
io_vsdl:
	push	dx			; save count and console no.
	push	bx			; save address in screen buffer.
	mov	bx,offset inslin	; bx = adr of insert line seq.
	call	io_vseq			; insert line on physical CRT.
	pop	bx			;aracter.
	call	divirt			; di = virtual console number * 2.
	call	io_vsad			; bx = address in buffer.
	mov	ah,1[bx]		; ah = attribute there.
	call	io_vatr			; change attribute if different.
	pop	cx			; cl = character to write.
	call	io_vck			; check cursor for bottom right.
	jnc	io_vwsx			; exit if at bottom right.
	mov	dl,0			; use console 0 for now.
	jmp	io_conout		; write character to console.
io_vwsx:
	ret

	; Check cursor to see if it's at or past bottom right.
	; If not, exit with carry fry:  ah = attribute for this transfer.
	; Exit:  vidatr is set if changed.
io_vatr:
	cmp	ah,vidatr		; same attribute as before?
	je	io_vatx			; exit if so.
	push	ax			; save ax.
	push	bx			; save bx.
	push	cx			; save cx.
	push	si			; save si.
	push	es			; save es.
	mov	vidatr,ah		; save new attribute byte.
	test	ah,08h			; is bright bit (3) set?
	mov	bx,offset setbrt	; default is set bright.
	jnz	io_vasa			; hop if bright bit high.
	mov	bx,offset setdim	; else bx = set dim seq adr.
io_vasa:
tents of video buffer.
	; Entry: bx = location in buffer.
	;	 di = virtual console number times 2.

io_vbdd:				; enter with insert line adr in0di.
	if	vcsbuf			; if virtual console screen buffer.
	push	ax			; save ax, cx.
	push	cx
	push	di			; save address of line to clear.
	push	bx			; save screen buffer address.
	mov	ax,cs			; get segmut we're in.
	mov	es,ax
	mov	cx,nochrs		; cx = number of screen chars.
	shl	cx,1			; cx = number of screen bytes.
	mov	di,scbuft[di]		; di = top of buffer ad	al,bh			; al = row.
	mov	bh,nocols		; bh = number of columns.
	mul	bh			; ax = address of row.
	shl	ax,1
	mov	bh,0			; bx = column.
	shl	bx,1			; bx = adr offset into row.
	add	ax,bx			; ax = location of character.
	mov	bx,scbuft[di]		; bx = screen buffer address.
	add	bx,ax			; bx = address of character.
	pop	ax			; restore ax.
	ret

	; Send sequence of control codes at bx to video screen.
	; Add in ch and cl to codes that have bit 7 set.
	; Do not update screen buffer.
io_vseq:
	mov	ah,[blag set.
	; If so, exit with carry flag clear.

io_vck:
	push	ax			; save ax.
	mov	ax,curpos[di]		; al = current column number.
	mov	ah,nocols		; ah = number of columns.
	dec	ah			; ah = last column number.
	cmp	al,ah			; is cursor at or past last col?
	jc	io_vckx			; exit if not.
	mov	ax,curpos[di]		; ah = current row number.
	mov	al,norows		; al = number of rows.
	dec	al			; al = last row number.
	cmp	ah,al			; is cursor at or past last row?
io_vckx:
	pop	ax			; restore ax.
	ret

	; Send
	call	io_vseq			; send sequence to CRT.
	pop	es			; restore es.
	pop	si			; restore si.
	pop	cx			; restore cx.
	pop	bx			; restore bx.
	pop	ax			; restore ax.
io_vatx:
	ret

	; Scroll up contents of screen buffer.
io_vbup:
	mov	bx,scbuft[di]		; bx = screen buffer address.
io_vbud:				; enter with starting adr in di.
	if	vcsbuf			; if virtual console screen buffer.
	push	ax			; save ax.
	push	cx			; save cx.
	push	di			; save virtual console * 2.
	mov	ax,cs			; get segment we're in.
	mov	dress.
	add	di,cx			; di = 1 byte past end of buffer.
	sub	di,2			; di = address of last word.
	mov	si,di			; si = address of last word.
	mov	al,nocols		; ax = number of words in a line.
	mov	ah,0
	shl	ax,1			; ax = number of bytes in a line.
	sub	si,ax			; si = last word of (last line-1).
	pop	ax			; ax = adr of line to insert.
	push	ax			; save it back.
	mov	cx,si			; cx = bottom word to move.
	add	cx,2			; cx = past bottom word.
	sub	cx,ax			; cx = number of bytes to move.
	shr	cx,1			; cx =x]			; get character count.
	cmp	ah,0			; can it be done on this terminal?
	je	io_vseqx		; exit if not.
	test	ah,80h			; is bit 7 of first byte set?
	jz	io_vseql		; hop into loop if not.
	and	ah,7fh			; else clear bit 7.
	xchg	cl,ch			; exchange row and column.
io_vseql:
	inc	bx			; point at next character.
	push	ax			; save counter.
	mov	al,[bx]			; get next character.
	test	al,80h			; should we add to code?
	jz	io_vseqs		; hop to send if not.
	and	al,7fh			; else clear bit 7.
	add	al,ch			;  character in al to console 0, ignore control characters,
	; check for bottom right, and don't update screen buffer.
io_vonc:
	cmp	al,20h			; is it a control character?
	jc	io_vonx			; exit if so.
	call	io_vck			; is it at bottom right?
	jnc	io_vonx			; exit if so.

	; IO_VONU - Send character to console, no screen buffer update.
	; Entry: al = character.
	;	 dl = physical console number.
	; Preserve ax, bx, cx, dx, si, and di.
io_vonu:
	push	ax			; save ax.
	push	bx			; save bx, cx.
	push	cxes,ax			; set for move.
	mov	al,nocols		; ax = number of words to next line.
	mov	ah,0
	shl	ax,1			; ax = no. of bytes to next line.
	mov	si,bx			; si = address of first line.
	add	si,ax			; si = address of next line.
	mov	cx,nochrs		; cx = number of screen chars.
	shl	cx,1			; cx = number of bytes in buffer.
	add	cx,scbuft[di]		; cx = 1 byte past end of screen.
	mov	di,bx			; di = screen buffer address.
	push	cx			; save end of screen address.
	sub	cx,si			; cx = number of bytes to move.
	shr	c number of words to move.
	std				; auto-decrement si, di.
	rep	movsw			; slide all but first line down.

	; clear out top line.
	mov	ah,vidatr		; ah = video attribute.
	mov	al,20h			; al = space.
	pop	di			; di = address of line to clear.
	mov	cl,nocols		; cx = number of words to write.
	mov	ch,0
	cld				; auto-increment di.
	rep	stosw			; make top line all spaces.
	pop	di			; di = virtual console * 2.
	pop	cx			; restore cx, ax.
	pop	ax
	endif

	ret

	; es = screen parameter structure sadd row or column.
	xchg	cl,ch			; exchange row and column.
io_vseqs:
	call	io_vonu			; send to video screen.
	pop	ax			; restore counter.
	dec	ah			; decrement counter.
	jnz	io_vseql		; loop back if more.
io_vseqx:
	ret


	; IO_KEYBD	KEYBOARD MODE
	; Enable/Disable PC-MODE.
	; Entry:
	;	al = 20h (32)
	;	cl = 1 for enable, cl = 2 for disable
	;	dl = virtual console number
	; Exit:
	;	ax = 0 if ok, ax = 0ffffh if error.
	;	es, ds, ss, sp preserved.

io_keybd:
	mov	pcflag,cl	; store pc-m
	push	dx
	push	si
	push	di			; save console no.
	mov	cl,al			; character was in al.
	call	io_conu			; output character in cl.
	pop	di			; restore console no.
	pop	si
	pop	dx
	pop	cx			; restore cx, bx.
	pop	bx
	pop	ax			; restore ax.
io_vonx:
	ret

	; Print message: "Graphics not implemented."
io_vgni:
	mov	bx,offset gnimsg	; bx = message address.
	call	prtmsg			; print message.
	jmp	io_ret			; print function, subfunction no.

	; If the video attribute has changed, set new one.
	; Entx,1			; cx = number of words to move.
	cld				; set to auto-incrment si, di.
	rep	movsw			; slide all up from si down.

	; clear out bottom line.
	pop	di			; di = end of buffer address.
	sub	di,ax			; di = address of bottom line.
	mov	ax,0f20h		; ax = attribute, character.
	mov	cl,nocols		; cx = number of words to move.
	mov	ch,0
	rep	stosw			; make bottom line all spaces.
	pop	di			; restore virt console * 2.
	pop	cx			; restore cx.
	pop	ax			; restore ax.
	endif

	ret

	; Scroll down conegment, si = offset.
	; dl = virtual console number.
io_vgp:
	mov	es,cx			; get parameter structure seg.
	mov	si,dx			; si = parameter structure offset.
	mov	dl,es:8[si]		; dl = virtual console number.
	ret

	; Get address of cursor in virtual screen buffer.
	; Entry: di = virtual console number * 2.
	;    curpos = column, row.
	; Exit: bx = address in screen buffer.
io_vsad:
	mov	bx,curpos[di]		; bh = row, bl = column.
io_vsab:				; for ext entry with bx=position.
	push	ax			; save ax.
	mov
	; Read DOS sector(s) defined by the IOPB.
	; Entry:
	;	al = 23h (35)
	;	DOS IOPB filled in (on stack)
	; Exit:
	;	al = 0 if no error
	;	al = 1 if physical error
	;	al = 0ffh if media density has changed
	;	ah = extended error code
	;	bx = ax
	;	es, ds, ss, sp preserved.

io_int13_read:
	jmp	io_read		; same except for head no in IOPB.

	; IO_INT13_WRITE	WRITE DOS SECTOR
	; Write DOS sector(s) defined by the IOPB.
	; Entry:
	;	al = 24h (36)
	;	DOS IOPB filled in (on stack)
	; Exit:
	;	aystem.
selflp:	push	si			; save drive number.
	mov	byte ptr diskno,0ffh	; force new controller setup.
	
	; Restore head to track 0 to read from that track.
	mov	al,cl			; al = drive number.
	mov	ah,stprat5+hlab		; ah = 5" restore command.
	test	al,4			; is it 5 or 8-inch?
	jz	selfcp			; hop if 5-inch.
	or	al,8			; set ENMF* bit.
	mov	ah,stprat8+hlab		; ah = 8" restore command.
selfcp:	mov	dx,fcont		; get floppy control port ad.
	out	dx,al			; tell controller which disk.
	mov	clatch,al		; save tlatch		; get current latch value.
	or	al,10h			; set to single density.
	mov	dx,fcont		; get latch port address.
	out	dx,al			; set floppy control latch.
	mov	clatch,al		; save the value.
	mov	dx,offset chkbuf	; get temporary buffer offset.
	mov	ax,cs			; get temporary buffer segment.
	call	comdma			; compute dma address.
	mov	cx,84d0h		; get 2793 read command.
	mov	dx,4080h		; get 128-byte dma read.
	mov	al,1			; read sector one.
	call	dmarw			; do dma read operation.
	jnz	selnr			; jump out if address of DPH.
	pop	bx			; bx = ptr to xlate table adr.
	mov	ax,[bx]			; get xlt table pointer.
	xchg	bx,dx			; bx=DPH adr, dx=code table adr.
	mov	[bx],ax			; put xlt pointer into dph table.

	; put Disk Parameter Block address into Disk Parameter Header.
	xchg	bx,dx			; dx=DPH adr, bx=code table ptr.
	add	bx,2			; bx = ptr to DBP address.
	mov	ax,[bx]			; ax = Disk Parameter Block adr.
	mov	bx,dx			; bx = Disk Parameter Header adr.
	add	bx,8			; bx = adr of DPB in DPH.
	mov	[bx],ax			; put Dl = 0 if no error
	;	al = 1 if physical error
	;	al = 0ffh if media density has changed
	;	ah = extended error code
	;	bx = ax
	;	es, ds, ss, sp preserved

io_int13_write:
	jmp	io_write	; same except head number in IOPB.


	; *********************************************************
	; *************     disk interface routines ***************
	; *********************************************************


	; Select disk.
	; Entry:  al = 9, cl = disk drive number,
	;	  dl bit 0 = 0 if first he value.
	mov	al,ah			; restore at fast step rate.
	mov	dx,fdisk		; get command port adr.
	out	dx,al			; start restore.
	call	waitio			; wait for completion.
	jz	selnr			; hop if disk not ready.
	mov	bx,(offset trtab)	; get address of track table.

	if	dual			; if persci drive
	and	cl,2			; index to 1 of 2 entries
	endif

	add	bx,cx			; add drive offset
	mov	byte ptr [bx],00h	; set to track 0
	mov	sektrk,0

	; First see if it's a 5-inch or 8-inch disk.
	test	cl,4			; is it an 8-inch drive? error during read.

	mov	al,chkbuf+7eh		; get Tarbell ID byte from buffer.
	or	al,al			; is it a zero?
	jnz	selnz			; hop if not.
	mov	al,0e5h			; big trouble for it to be zero.

	; Figure internal density code byte from disk code byte (in al).
	; Note that there are two kinds of density codes.  The one
	; that's in register al at this point is the one that comes
	; from the first track of the floppy disk itself.  The one
	; that's stored in dens is different, and is coded thusly:
	;   bit 0 = PB adr into DPH.

	; Save current sectors per track & physical sector shift.
selset:	mov	bx,ax			; bx = DPB address.
	cmp	word ptr [bx],0ffffh	; is it a PC-DOS DPB?
	jne	notpc			; hop if not.
	add	bx,12			; increment past extension if so.
notpc:	mov	al,psh[bx]		; get physical sector shift.
	mov	curpsh[si],al		; put in current psh table.
	mov	ax,[bx]			; ax = physical sectors per track.
	shl	si,1			; multiply by 2 for word table.
	mov	curspt[si],ax		; put in current spt table.
	mov	ax,dx			; ax =select.
	; Exit:  ax = offset of dph if no error,
	;	 ax = 0 if invalid drive,

io_seldsk:
	mov	ercode,0		; clear error code.
	mov	diskto,dsktim		; set disk time-out.
	mov	erdisk,cl		; save letter code (0-15).
	xor	ax,ax			; clear ax for possible error.
	mov	ch,0			; clear upper cx for index.
	mov	si,offset drvmap	; get drive map table address.
	add	si,cx			; figure address of entry.
	mov	cl,[si]			; get physical drive number.
	cmp	cl,0ffh			; is it undefined?
	jz	selex			; error to cpm if so.
	jnz	nonibm			; hop if so.

	; Next see if it's a 512-byte or 128-byte format.
	call	rdadrc			; read id into chkbuf.
	jnz	nonibm			; not 512 sectors if it can't.

	; must be 512-byte format.  could be CP/M-86 or PC-DOS format.
	mov	cx,094d0h		; ch = floppy read command.
	mov	dx,04400h		; dx = 1024-byte dma read.
	mov	al,1			; al = starting sector number.
	call	dmarw			; read 2 512-byte sectors.
	jnz	selnr			; exit if error.
	mov	al,chkbuf + 512		; ax = possible fat word.
	mov	ah,chkbuf + 513
1 for double density,
	;   bit 1 = 1 for double sided,
	;   bit 2 = 1 for 512-byte sectors.
	;   bit 3 = 1 for DR/IBM formats.
	;   bit 4 = 1 for PC-DOS formats.
selnz:
	mov	bx,(offset dpbt5)	; 5" dpb table address.
	mov	cl,sekdsk		; get drive number.
	test	cl,4			; is it 5-inch floppy?
	jz	selop			; hop if so.
	mov	bx,(offset dpbt8)	; 8" floppy dpb table address.
selop:
	cmp	byte ptr [bx],0		; is it last table entry (0)?
	je	setden			; hop out of loop if so.
	cmp	al,[bx]			; is it this densit Disk Parameter Header adr.
	ret

	; Get address of Disk Parameter Header in ax and dx.
	; Get internal disk number in si.
index:	xor	bh,bh			; load disk number and zero byte.
	mov	bl,sekdsk
	mov	si,bx			; put disk number in si.
	mov	dx,(offset dphtab)	; get disk param header table adr.
	shl	bx,1			; drive number times 2.
	add	bx,dx			; figure table entry address.
	mov	dx,word ptr [bx]	; get address of dph from table.
	mov	ax,dx			; put it in ax.
	ret				; return from seldsk (& other places).

	mov	si,cx			; si = internal disk number.
	mov	sekdsk,cl		; save new disk number.
	test	dl,fresh		; fresh access?
	jz	sellog			; skip if not logged in.
	jmp	index			; jump if already logged in.

selex:	ret				; error return to op sys.

	; This disk not logged in yet, so must do it.
sellog:	cmp	cl,8			; is it a hard disk drive?
	jc	selflp			; hop if not.
	jmp	selhrd			; jump if so.

	; This floppy disk is not logged in, so we must determine
	; it's size, sector length, format, and operating s
	cmp	ax,0fffch		; is it PC-DOS fat word?
	jnc	selnz			; hop if it is.

	; must be a DR/IBM (non-PCDOS) format for CP/M-86.
	mov	al,chkbuf + 511		; al = DR's id byte.
	inc	al			; let's not use zero.
	jmps	selnz			; hop to figure rest of it.

	; error encountered.
selnr:	pop	bx			; make stack right.
selnrh:	mov	al,3			; set select error code.
	call	recov			; print error message.
	mov	ax,0			; return bad select.
	ret

	; must not be ibm format, so read single density sector 1.
nonibm:	mov	al,cy code?
	je	setden			; hop out of loop if so.
	add	bx,6			; else to next code entry.
	jmps	selop			; try the next one.

	; set internal density code byte (dens).
setden:	inc	bx			; point at internal code byte.
	mov	al,[bx]			; get density byte from table.
	pop	si			; si = internal drive number.
	mov	dens[si],al		; set current drive density.

	; put translate table address into Disk Parameter Header.
	inc	bx			; point at xlate table address.
	push	bx			; save table pointer.
	call	index			; dx = - Get hard disk error parameters from registers.
iogete:
	mov	ercyl,bx		; error cylinder.
	mov	erhead,ch		; error head.
	mov	ersect,dl		; error sector.
	mov	ercode,ah		; error status.
	ret
	endif

selmap:	call	mapper			; log in hard disk drive.
	jc	selher			; hop if error.
selner:	call	index			; ax, dx = DPH address.
	add	ax,8			; ax = pointer to DPB.
	mov	bx,ax			; bx = pointer to DPB.
	mov	ax,[bx]			; ax = address of DPB.
	jmp	selset			; set spt, psh, return with dph adr.

selher:	jmp	sedskss = old stack segment.
	mov	dsksp,sp		; dsksp = old stack pointer.
	mov	ax,ds			; stack segment = data segment.
	mov	ss,ax
	mov	sp,offset dskstk	; stack pointer = disk stack.
	mov	ax,offset dskret	; put return address on new stack.
	push	ax

	cmp	mcnt,0			; is multisector count=0?
	jne	io_dlp
	jmp	io_dbc			; exit with bad command error.
io_dlp:
	mov	diskto,dsktim		; set disk time-out timer.
	mov	dl,drive		; dx = logical drive number.
	mov	dh,0
	mov	erdisk,dl		; save it for error print-outent sector number.
	shr	si,1			; now it's a byte table.
	mov	cl,7			; track 0 default.
	cmp	trk0,true		; track 0 flag true?
	je	io_t0			; hop if so.
	mov	cl,curpsh[si]		; get sector shift factor.
	add	cl,7			; adjust. 128-byte psh = 0.
io_t0:	shl	dx,cl			; multiply by bytes/sector.
	mov	bytcnt,dx		; save byte count.

	; decide whether floppy or hard disk, then make transfer.
	if	nhard gt 0		; if one or more hard disks.
	cmp	sekdsk,8		; is it a hard disk transfer?
	jc	io_tfl			; hop if floppy.
,0101h		; return bad command error.
io_dex:	ret

	; other errors.
io_rec:	mov	al,oper			; al = operation code.
	call	recov			; print error message.
	mov	ax,0110h		; crc code for now.
	ret


	; Do read or write from/to floppy disk at current track.
	; Multiple sectors on same track are allowed.
	; Set or clear write-precompensation bit as needed.
	; This is where the error retry is performed.
	; Actual transfer is done in subroutine dmarw.
	; Entry:  ax = starting sector number
	;	  dx = numblnrh			; print error message & return.
	endif

	; Read the next id field into chkbuf.

rdadrc:	mov	dx,offset chkbuf	; dx = destination offset.
	mov	ax,cs			; ax = destination segment.
	call	comdma			; compute dma adr (lsb20,msb20).
	mov	cx,0c4d0h		; read address code.
	mov	dx,04006h		; disk-memory, 6 bytes.
	jmp	dmarwe			; read 6 bytes into chkbuf.


	; IO_READ and IO_WRITE
	; Read sector and Write sector.
	; Note:  io_init13_read and io_init13_write come here too.
	; Entry:
	;	al = 0ah (10.
	mov	si,dx			; si = drive number from os.
	mov	dl,drvmap[si]		; dx = internal drive number.
	mov	sekdsk,dl		; save for dmarw poll.
	mov	cx,track		; get track # in cx.
	call	seekls			; seek the disk to the proper track.
	jz	io_dok			; hop if good seek.
	ret				; else return with seek error.

	; restore stack for common return from disk i/o.
dskret:	mov	ss,dskss		; restore stack segment.
	mov	sp,dsksp		; restore stack offset.
	ret

io_dok:	mov	dx,dmaoff		; get destination offset.
	mov	ax,dmas
	if	ades			; if ADES controller.
	cmp	sekdsk,12		; is it for ADES controller?
	jc	ionad			; hop if not.
	mov	es,dmaseg		; es = transfer segment.
	mov	di,dmaoff		; di = transfer offset.
	mov	bx,track		; bx = cylinder number.
	mov	cx,nosecs		; cx = number of sectors to transfer.
	mov	dx,sector		; dx = starting sector within cylinder.
	mov	al,sekdsk		; al = logical drive number.
	sub	al,12			; make 0-3 for ADES controller.
	mov	ah,oper			; ah = 1 for read, 2 for write.
	call	ad_th			; call ADES drer of bytes to transfer
	; Exit:	  ZF set if no error.

io_tf:	mov	diskto,5		; set disk time-out counter.
	cmp	oper,1			; is it a read operation?
	je	io_rd			; hop if so.

	; must be write transfer - make write-precompensation bit right.
	push	dx			; save byte count and sector number.
	push	ax
	mov	dx,ftrk			; dx = track register port.
	in	al,dx			; al = current physical track number.
	cmp	al,pctrk		; do we need pre-compensation?
	mov	al,clatch		; al = current latch value.
	jc	io_tfn			; hop i) for io_read
	;	al = 0bh (11) for io_write
	;	al = 23h (35) for io_init13_read
	;	al = 24h (36) for io_init13_write
	;	IOPB on stack has parameters as noted above.
	; Exit:
	;	al = 0 if no error
	;	al = 1 if physical error
	;	al = 0ffh if media density has changed
	;	ah = extended error code
	;	bx = ax

io_read:
	mov	oper,1			; read operation.
	jmps	io_disk			; now do common disk routine.

io_write:
	mov	oper,2			; write operation.

	; Perform disk i/o transfer.
io_disk:
	mov	ercode,0	eg		; get destination segment.
	call	comdma			; compute physical dma adr.

	; get internal drive number into si to index into tables.
	mov	al,sekdsk		; get drive number.
	mov	ah,0
	mov	si,ax
	shl	si,1			; curspt word table is first.

	; figure number of sectors to ask controller to transfer.
	mov	ax,sector		; get starting sector to transfer.
	mov	cx,ax			; save in cx.
	mov	dl,mcnt			; get multi-sector count.
	mov	dh,0
	cmp	trk0,true		; track zero flag true?
	je	io_tz			; hop if so.
	add	ax,diver.
	jnc	iotok			; hop if no errors.
	call	iogete			; get error parameters from registers.
	jmps	io_rec			; print error message and return.
	endif

ionad:	call	io_th			; do hard disk transfer.
	jmps	io_der			; check for errors.
	endif

io_tfl:	call	io_tf			; do floppy disk transfer.

	; check for error, see if more to do.
io_der:	jnz	io_rec			; exit if transfer error.

	; see if there's more multi sectors to transfer.
iotok:	mov	ax,mlft			; update multi-sector count.
	mov	mcnt,al
	cmp	axf no precomp needed.
	or	al,20h			; else set bit 5 of latch.
	jmps	io_tfs			; set latch.
io_tfn:	and	al,0dfh			; clear bit 5 of latch.
io_tfs:	mov	dx,fcont		; dx = latch port address.
	out	dx,al			; set the latch.
	mov	clatch,al		; remember what's there.
	pop	ax			; restore sector number and byte count.
	pop	dx

	; set up for write transfer.
	mov	cx,0b4d0h		; floppy write, force interrupt cmds.
	or	dx,08000h		; dma write, dma count byte cmds.
	jmps	io_tr			; do transfer.

	; set up for read t	; clear any old error codes.
	mov	bp,sp			; get stack address.

	; get parameters for transfer from stack.
	mov	al,19[bp]		; mcnt = multi-sector count.
	mov	mcnt,al
	mov	al,18[bp]		; drive = drive number.
	mov	drive,al
	mov	ax,16[bp]		; track = cylinder number.
	mov	track,ax
	mov	ax,14[bp]		; sector = sector number.
	mov	sector,ax
	mov	ax,12[bp]		; dmaseg = transfer segment.
	mov	dmaseg,ax
	mov	ax,10[bp]		; dmaoff = transfer offset.
	mov	dmaoff,ax

	; set up local stack.
	mov	dskss,ss		; x			; what would be the last sector?
	dec	ax			; make comparison work.
	sub	ax,curspt[si]		; is it past end of track?
	jnc	io_tend			; hop if past end of track.
io_tz:	mov	ax,-1			; multi-count will be zero.
io_tend: inc	ax			; set new multi-sector count.
	mov	mlft,ax			; this is the count left.
	sub	dx,ax			; sectors for THIS transfer.
	mov	nosecs,dx		; save number of sectors to do.

	; now get ready to do the transfer operation.
	mov	ax,cx			; restore starting sector number.
	inc	ax			; increm,0			; any multi-sectors left?
	je	io_dex			; exit if not.
	mov	sector,0		; start with first sector,
	inc	track			; since it must be new track.
	mov	ax,bytcnt		; add byte count to dmaoff.
	add	dmaoff,ax
	jc	io_dec			; hop if add overflowed.
	jmp	io_dlp			; loop back for some more.

io_dec:	add	dmaseg,1000h		; add carry into segment.
	jmp	io_dlp			; loop back for some more.

	; zero sector count error.
io_dbc:	mov	al,oper			; al = current operation.
	call	recov			; print error message.
	mov	axoper			; al = current operation.
	call	recov			; print error message.
	pop	bx			; restore error code.
io_trx:	mov	ax,bx			; ax = error code.
	or	al,al
	ret


	; disk error handler: on entry al = error type.
	;   print type, track, sector, & status.

recov:
	push	ax			; save error flag.
	mov	bx,(offset errmsg)
	call	prtmsg			; error intro message.
	pop	ax			; get flag back.
	xor	ah,ah			; clear high bits.
	mov	cl,7			; table offset.
	mul	cl			; multiply by offset.
	inc	bx			; past eom.
	aov	cl,dl			; get bcd value.
	add	cl,'0'			; add ascii bias.
	call	conout			; print the digit.
	pop	dx			; recover next bcd value.
	ret				; print all digits recursivly.

;
; SEEKLS - Seek selected floppy disk to track.
; If hard disk, just return.  Seek will be done in io_th.
; If floppy disk, seek drive dl to track in cl.
; If ch <> 0 then must be PC-DOS disk head number.
; Set latch with correct density, drive, and side code.
; Update track table if the track has changed.
; Perform read id fu	mov	al,dens[si]		; get density type byte.

	; figure whether to treat this track special.
	test	al,00011000b		; 512-byte sectors on track 0?
	jnz	seeka			; hop ahead if so.
	cmp	bl,0			; are we on track zero?
	jne	seeka			; hop ahead if not.
	mov	trk0,true		; else set track 0 flag true.

seeka:	test	al,00010000b		; is it a PC-DOS disk?
	jnz	seekpc			; hop if so.

	test	al,00001000b		; is it a DR/IBM for CP/M-86?
	jz	seekni			; hop if not.

	; must be Digital Research format for CP/M-86 on IBnew track number?
	jnz	nothr			; nope, go move it.
	pop	cx			; restore cx.
	xor	ax,ax			; return no error flags.
	ret				; return from seek.

nothr:
	; note: this routine is to allow time for the drive
	;	tunnel erase to terminate before moving the
	;	head.  the delay is aprx. 700 micro-seconds.

	mov	al,0			; delay count = 256.
busy1:
	dec	al			; decrease count.
	jnz	busy1			; loop till zero.

	mov	al,cl			; put dest. in al from cl.
	mov	dx,fdata		; get data port adr.
	out	dx,al			; trackdd	bx,ax			; add offset.
	call	prtmsg			; print the error type.
	mov	bx,(offset drvmsg)
	call	prtmsg			; drive message.
	mov	cl,erdisk		; cl = crive letter code.
	add	cl,'A'			; make into actual letter.
	call	conout			; print the letter.
	inc	bx			; past eom.
	call	prtmsg			; cylinder message.
	mov	cx,ercyl		; get current cylinder #.
	call	decout			; print in decimal.
	inc	bx			; past eom.
	call	prtmsg			; print 'head'.
	mov	cl,erhead		; cl = head number.
	call	prtdec			; print it.
	inc	bx			nction to recalibrate disk if seek error.
; Exit:	z clear if error, set if no error.
;
seekls:
	mov	trk0,false		; assume no special treatment.
	cmp	sekdsk,8		; is it floppy or hard disk?
	jc	seeklf			; hop if floppy.
	xor	ax,ax			; set z flag, return no errors.
	ret

seeklf:	mov	diskto,5		; set disk time-out counter.
	cmp	byte ptr diskno,dl	; test for new drive
	jz	samedsk			; not a new drive so just seek.

	mov	byte ptr diskno,dl	; update current disk #

	; new drive so get present track anM-PC.
	and	bh,0efh			; clear single density bit.
	cmp	bl,ibmtpd		; is track greater than 39?
	jc	trksd5			; hop if not.
	mov	al,2*ibmtpd-1		; subtrack track no. from 79.
	sub	al,bl
	mov	bl,al
	or	bh,40h			; set side select bit.
	jmps	trksd5			; finish below.

seekni:	or	bl,bl			; is it track zero?
	jz	trksd			; hop if so.

seekpc:	test	al,2			; test for double sided
	jz	trkss			; don't /2 if single sided

	; figure track to go to and which side to select.
	test	bl,1			; is it an even track  to data register.

	; get the seek command with correct step rate.
	mov	al,14h+stprat5+hlab	; al = 5" seek command.
	cmp	sekdsk,4		; is it a 5" or 8" floppy?
	jc	seekt			; hop if 5-inch.
	mov	al,14h+stprat8+hlab	; al = 8" seek command.
seekt:	mov	dx,fdisk		; get command port adr.
	out	dx,al			; set rate, seek with verify.
	call	waitio			; poll process complete.
	jz	sknr			; hop if not ready error.

	mov	dx,fdisk		; get status port adr.
	in	al,dx			; read status.
	mov	ercode,al		; save status ; past eom.
	call	prtmsg			; sector message.
	mov	cl,ersect		; get current sector #.
	call	prtdec			; print in decimal.
	inc	bx			; past eom.
	call	prtmsg			; status message.
	mov	ah,ercode		; get status bits.
	mov	ch,8			; eight bits in status.

bitlop:
	mov	cl,'0'			; assume bit is 0.
	rol	ah,1			; test next bit.
	jnc	prtbit			; it's off, leave 0.
	inc	cl			; it's on, make 1.

prtbit:
	call	conout		; print bit value.
	dec	ch			; dec bit counter.
	jnz	bitlop			; print all bits.
	ret


d seek to it to
	; to inform the controller that the head is unloaded.

	push	dx			; save dx.
	mov	dx,ftrk			; get track register port.
	in	al,dx			; read track register.
	mov	dx,fdata		; get data port.
	out	dx,al			; send track to data port.
	mov	al,10h			; get seek command no verify
	mov	dx,fdisk		; get command port adr.
	out	dx,al			; do the (non) seek.
	call	waitio			; wait till done
	pop	dx			; restore dx.
	jnz	samedsk			; hop if disk was ready.
	jmp	sknr2			; seek not ready error.

	; no?
	jz	trkev			; hop if so.
	or	bh,40h			; or in side select if not.
trkev:	shr	bl,1			; divide track by 2.

trkss:	test	al,1			; test for double density
	jz	trksd			; hop if single density.
	and	bh,0efh			; clear single density bit.
trksd:	test	dl,4			; is it 5 or 8-inch floppy?
	jz	trksd5			; hop if 5-inch floppy.
	or	bh,8			; set weird bit 3 if 8-inch.
trksd5:	mov	al,bh			; get density-select code
	mov	dx,fcont		; get floppy control port.
	out	dx,al			; set up the latch.
	mov	clatch,al		; bits.
	test	al,91h			; look at success bits.
	jnz	skerr			; zero if ok.
	pop	cx			; recover cx.
	mov	dx,diskno		; get drive index

	if	dual			; if using persci drives.
	and	dl,2			; index to 1 of 2 entries
	endif

	mov	bx,(offset trtab)	; point at track table
	add	bx,dx			; add index
	mov	[bx],cl			; update track table
	xor	ax,ax			; set z flag, return no errors.
	ret				; return seek ok.

	; error handling.
skerr:
	dec	sercnt			; decrement error counter.
	jnz	sretry			; retry if not zero
	; convert cl to decimal and display at console.

prtdec:
	xor	ch,ch			; clear top eight bits.
decout:
	push	dx			; save value on stack.
	mov	dx,-1			; this becomes number / radix.

sub10:
	sub	cx,10			; subtract 10.
	inc	dx			; inc remainder.
	jnc	sub10			; loop till carry out.
	add	cx,10			; add radix back in.
	xchg	dx,cx			; switch new/current.
	test	cx,cx			; test for zero reminder.
	jz	cndone			; if zero, conversion complete.
	call	decout			; build bcd digits recursivly.

cndone:
	msetup density & such
samedsk:
	xor	dh,dh			; clear dh
	mov	si,dx			; save drive number.

	if	dual			; if persci drive
	and	dl,2			; index to 1 of 2 entries
	endif

	mov	bx,offset trtab		; get track table adr.
	add	bx,dx			; get address in table.
	mov	al,[bx]			; get old track #.
	mov	dx,ftrk			; get track port adr.
	out	dx,al			; update track register.

	mov	bl,cl			; save track # in bl
	mov	dl,byte ptr diskno	; get drive #
	or	dl,10h			; set single density bit.
	mov	bh,dl			; save in bh
save the value.

	; set erhead for error routine.
	test	al,40h			; is it head 1?
	mov	al,0			; default is zero.
	jz	headst			; hop if head zero.
	inc	al			; inc if head 1.
headst:	mov	erhead,al		; set head number for error routine.
	mov	cl,bl			; put track in cl.

	; perform actual seek to track given by cl.

seek:
	push	cx			; save cx.
	mov	sercnt,srtcnt		; reset seek retry error counter.
	mov	dx,ftrk			; get track register port.
	in	al,dx			; read present track no.
	cmp	al,cl			; same as al = restore at 8-inch rate.
sretr2:	mov	dx,fdisk		; get status port.
	in	al,dx			; read status.
	call	waitio			; wait for completion.
	jz	sknr			; hop if seek not ready error.
	jmps	chks2			; go re-seek track.

chks1:
	mov	dx,fsect		; get floppy sector port.
	in	al,dx			; read sector.
	mov	dx,ftrk			; get floppy track port.
	out	dx,al			; re-inform controller of proper track.

chks2:
	pop	cx			; restore track #.
	jmp	seek			; move head to it.


; Common floppy DMA read & write subroutine.v	dx,dmadpl0		; get dest lower port.
	out	dx,ax			; set destination lower.
	mov	ax,cx			; get source lower.
	mov	dx,dmaspl0		; get source lower port.
	out	dx,ax			; set source lower.

	; set dma count and command.
	pop	bx			; restore read or write comd.
	pop	ax			; restore transfer count.
	and	ah,3fh			; clear old command bits.
	mov	dx,dmatc0		; get transfer count port.
	out	dx,ax			; set transfer count.
	mov	ax,bx			; get read or write command.
	mov	dx,dmacon0		; get dma control port.
	out	dxrd not found error?
	jz	dmaer3			; hop if not.
	or	bh,4h			; set if so.
dmaer3:	test	al,8			; crc error?
	jz	dmaer4			; hop if not.
	or	bh,10h			; set crc bit for bdos.
dmaer4:	test	al,1			; is controller still busy?
	jz	dmaer5			; hop if not.
	or	bh,20h			; controller failed if so.
dmaer5:	or	bl,bl			; clear z flag for error return.
	ret


	; Wait until last floppy disk operation is complete.
	; If disk is not ready, exit with al=0, Z status flag set.
	; If disk is ready, exit back to CCPM Xal.
	ret
	endif

seeksf:	mov	dx,fdisk		; get floppy status port.
	in	al,dx			; read status.
	and	al,1			; is busy bit set?
	jz	seekex			; hop if not busy.
	mov	al,0ffh			; will be 0 for busy.
seekex:	not	al			; this makes it all ok.
	mov	bl,al
	ret


	; Provide a delay after commands for status to become valid.

fdelay:	push	cx			; save cx.
	mov	cx,80h			; this seems to work.
fdloop:	loop	fdloop			; count down till cx=0.
	pop	cx			; restore cx.
	ret

	; Disk time-out error.
diskte:
	
; Entry:  ch = command to write to floppy controller chip.
;	  dh upper 2 bits = dma operation code.
;	    if bit 7 = 0, read operation, 1 for write.
;	  dx lower 14 bits = number of bytes to transfer.
;	  al = sector number

dmarw:
	; set floppy sector register from sect.
	mov	ersect,al		; save sector # for error message.
	push	dx			; save dx.
	mov	dx,fsect		; get sector port adr.
	out	dx,al			; set sector number.
	pop	dx			; restore dx.

dmarwe:
	push	cx			; save cx.
	push	dx			; save dx,ax			; initialize dma operation.

	; start floppy controller running.
	pop	cx			; restore floppy read/write comd.
	mov	al,ch			; get floppy read/write command.
	mov	dx,fdisk		; get floppy command port adr.
	out	dx,al			; start read or write operation.
	cmp	al,0c4h			; was it a read address?
	je	dmarda			; hop if so.
	mov	dl,sekdsk		; get physical drive number.
	or	dl,5 shl 5		; set operation category 5.
	call	wait			; wait until it's done.
	mov	al,80h			; al = not ready code.
	jz	dmaex			; exiDOS until op done.
	; Then exit with al = 0ffh, Z status flag clear.

waitio:
	call	fdelay			; wait for valid status.
	push	dx			; save dx.
	mov	dx,fdisk		; get floppy status port.
	in	al,dx			; read status.
	and	al,80h			; is the disk even ready?
	jnz	waitnr			; hop if disk not ready.
	mov	dl,sekdsk		; dl = physical drive number.
	or	dl,6 shl 5		; set poll category = 6.
	call	wait			; wait until operation done.
	jz	waitnr			; hop if time-out error.
	mov	al,0ffh			; set device ready flag.
	ormov	ercode,80h		; set not-ready error code.
	mov	al,0ffh			; return with ready status.
	mov	bl,al
	ret

	; poll for current disk dma activity completed.
	; Exit:  al = 0 if not ready.
	;	 al = ff if ready.
	;	 bl = al.

diskst:
	cmp	diskto,0		; is time-out down to zero yet?
	je	diskte			; time-out error if so.

	if	nhard gt 0		; if one or more hard disks.
	cmp	sekdsk,8		; is it hard or floppy disk?
	jnc	seeksh			; jump if hard disk.
	endif

	mov	dx,dmatc0		; get transfer count port.
	in	.
	mov	dx,fdisk		; get floppy status port.
	in	al,dx			; read floppy status.
	test	al,80h			; is floppy ready?
	jnz	dma_xt			; hop out if not ready.

	; get floppy port address and memory transfer address.
	mov	al,msb20		; get 4 hi bits of adress.
	mov	ah,0			; get 4 hi bits of floppy port.
	mov	bx,lsb20		; get 16 lo bits of address.
	mov	cx,fdata		; get 16 lo bits of floppy port.
	pop	dx			; get command flag and count.
	push	dx			; save it back.
	test	dh,80h			; is it a write or read op?
	movt if time-out.
	call	fdelay			; let crc bytes get written.
	mov	dx,fdisk		; get floppy command port.
	mov	al,0d0h			; issue force interrupt command.
	out	dx,al
dmarda:
	call	waitio			; wait until 2793 not busy.
	mov	al,80h			; al = time-out code.
	jz	dmaex			; exit if time-out.
	push	cx			; make stack right.
	push	dx
	mov	dx,fdisk		; get status port.
	in	al,dx			; read status.
dma_xt:
	pop	dx			; restore dx,cx.
	pop	cx
dmaex:
	mov	ercode,al		; save status code.
	and	al,99h			; look at erro	al,al
	pop	dx			; restore dx.
	ret
waitnr:
	xor	al,al			; set not ready flag.
	pop	dx			; restore dx.
	ret				; return from waitio.


	; Determine whether a disk controller operation is done.
	; Assumes that initial status valid delay was done above.
	; Entry:  dl = logical drive number.
	; Exit:  al = 0ffh if operation complete.
	;	 al = 0 if operation not complete.
	;	 bl = al.

seekst:
	cmp	diskto,0		; is time-out down to zero yet?
	je	diskte			; time-out error if so.

	if	nhard gt 0ax,dx			; read count register.
	test	ax,ax			; is it zero yet?
	jz	diskstex		; exit ready if so.
	mov	al,0ffh			; so al=0 on exit for not ready.
diskstex:
	not	al			; make it right.
	mov	bl,al			; make bl same as al.
	ret


	; Flush Buffers.
	; Since there are currently no buffers internal to
	; this XIOS, this routine doesn't have to do anything.

io_flushbuf:
	mov	ax,0			; set no error.
	mov	bx,ax			; make bx same as ax.
	ret				; return.


	; Dummy I/O Return.
io_ret:
	push	bx			; s	dx,fdmard		; get dma read command.
	jz	dmard			; must be read if bit 7=0.

	xchg	al,ah			; exchange source and dest ptrs.
	xchg	bx,cx
	mov	dx,fdmawt		; get dma write command.
dmard:	push	dx			; save on stack.

	; at this point:  destination=bx,al;  source=cx,ah.
	mov	dx,dmadpu0		; get dest upper port.
	out	dx,ax			; set destination upper.
	mov	al,ah			; get source upper in al.
	mov	dx,dmaspu0		; get source upper port.
	out	dx,ax			; set source upper.
	mov	ax,bx			; get destinaiton lower.
	mor bits.
	jnz	dmaer			; hop if error in dmarw.
	xor	bx,bx			; else show no error.
	ret				; return from dma common.

	; error detected in dmarw routine.
	; convert error bits from 2793 to error bits for operating system.
dmaer:	mov	bx,1			; initialize error flag.
	test	al,80h			; was it not ready?
	jz	dmaer1			; hop if not that bit.
	or	bh,80h			; else set respond bit.
dmaer1:	test	al,40h			; was it write-protected?
	jz	dmaer2			; hop if not.
	or	bh,3			; set if so.
dmaer2:	test	al,10h			; reco		; if one or more hard disks.
	cmp	sekdsk,8		; is it floppy or hard disk?
	jc	seeksf			; hop if floppy.
seeksh:
	if	ades			; if ADES controller.
	cmp	sekdsk,12		; is it ades?
	jc	seeksk			; hop if so.
	mov	ah,3			; ah = code to check status.
	call	ad_th			; call ades hard disk driver.
	jmps	seekso			; do rest below.
	endif
seeksk:
	cmp	dmastat,0		; is hard disk busy?
seekso:	mov	al,0			; set al to busy.
	je	seeksx			; exit if busy.
	not	al			; set al to complete.
seeksx:	mov	bl,al			; bl = if Rodime-20.
	include	w20
	endif

	if	min20			; if Miniscribe 4020.
	include	wm4020
	endif

	if	ota26			; if Otari C-526.
	include	wo526
	endif

	if	ats33			; if Atasi 33.
	include w33
	endif

	if	q540			; if Quantum Q540.
	include	wq540
	endif

	if	morrow		; if morrow hard disk controller.
	include	morhdc
	endif

	if	teletek		; if teletek hard disk controller.
	include	telhdc
	endif

	if	ades		; if ADES hard disk controller.
	include	ades33
	endif

	endif

;*********** ENr,lf
	endif
	if	nhard gt 0
	if	morrow
	db	'  Morrow'
	endif
	if	teletek
	db	'  Teletek'
	endif
	db	' controller with '
	if	rms12			; if RMS-12.
	db	'RMS-12'
	endif
	if	cmi19			; if CMI-19.
	db	'CMI-19'
	endif
	if	rod20			; if Rodime-20.
	db	'Rodime-20'
	endif
	if	min20			; if Miniscribe 4020.
	db	'Miniscribe 4020'
	endif
	if	ota26			; if Otari C-526.
	db	'Otari C-526'
	endif
	if	ats33			; if Atasi-33.
	db	'Atasi-33'
	endif
	if	q540			; if Quantum Q540.
	db	'Quantum Q-540'
	endi0			; dma abs bits a00-a15.
sekdsk	db	0			; selected logical disk.
sektrk	dw	0			; track to seek to.
mlft	dw	0			; sectors left to transfer.
bytcnt	dw	0			; bytes left to transfer.
nosecs	dw	0			; number of sectors to transfer.
diskto	rb	1			; disk time-out counter.

	; disk (hard and floppy) parameters for error message only.
erdisk	db	0			; drive letter 0-15.
ercyl	dw	0			; physical drive cylinder.
erhead	db	0			; head 0-7.
ersect	db	0			; sector number.
ercode	db	0			; error status.

	; Lo endif	; hard disk 4.
	if nhard gt 5! dw offset dph13! endif	; hard disk 5.
	if nhard gt 6! dw offset dph14! endif	; hard disk 6.
	if nhard gt 7! dw offset dph15! endif	; hard disk 7.
	if nhard gt 8! dw offset dph16! endif	; hard disk 8.
	if nhard gt 9! dw offset dph17! endif	; hard disk 9.
	if nhard gt 10! dw offset dph18! endif	; hard disk 10.
	if nhard gt 11! dw offset dph19! endif	; hard disk 11.


	; - 5-inch floppy diskette - unit 0.

dph0	equ	(offset $)

	if	nflop5 gt 0
	dw	0,0,0,0			;D OF HARD DISK DRIVER AREA ******************


	; bios data area.

data_offset	equ	(offset $)

	dseg

	org	data_offset		; start of data segment area.


	; PC-MODE VARIABLES

pcflag	db	2		; pc mode mode: 1=enabled, 2=disabled.
shflg	db	0		; shift flag.
scmode	db	1		; screen mode.  1 = general alphanumeric.
vidatr	db	0fh		; video attribute byte.


	; Address Table of Poll Device Routines.
	; Device numbers are allocated thusly:
	;	left 3 bits = category of device operation
	;	right 5 bf
	if	ades			; if ADES-33
	db	cr,lf,'  and ADES controller with PRIAM 3350'
	endif
	db	' hard disk',cr,lf
	endif
	db	0			; end of message.

trpmsg	db	cr,lf,7
	db	'XIOS detected undefined interrupt'
	db	cr,lf,0

funmsg	db	cr,lf,7,'Function ',0
submsg	db	', subfunction ',0
notmsg	db	' not implemented.',cr,lf,0
gnimsg	db	cr,lf,'Graphics not implemented',0

e6msg	db	cr,lf,7,'E6 INT',0

errmsg	db	cr,lf
	db	'error during ',0
	db	'seek: ',0		; error 0.
	db	'read: ',0		; error 1.
	db	'write:'gical (letter) to physical (number) drive map.
	; These should always stay in this order.  To change
	; the map, change the EQU's at the beginning of BIOS.

drvmap	db	drivea			; drive a number.
	db	driveb			; drive b number.
	db	drivec			; drive c number.
	db	drived			; drive d number.
	db	drivee			; drive e number.
	db	drivef			; drive f number.
	db	driveg			; drive g number.
	db	driveh			; drive h number.
	db	drivei			; drive i number.
	db	drivej			; drive j number.
	db	drivek			; drive k nu translate table, scratch.
	dw	f5sgen			; io_seldsk puts DPB address here.
	dw	0ffffh,0ffffh		; checksum, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif

	; 5-inch floppy unit 1.

dph1	equ	(offset $)

	if	nflop5 gt 1
	dw	0,0,0,0			; translate table, scratch.
	dw	f5dbds			; io_seldsk puts DPB address here.
	dw	0ffffh,0ffffh		; checksum, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif

	; 5-inch floppy unit 2.

dph2	equ	(offset $)its = number within category

polltbl	dw	io_const		;  0: console input.
	dw	io_pollco		;  1: console output.
	dw	io_listst		;  2: printer output.
	dw	io_pollai		;  3: aux input.
	dw	io_pollao		;  4: aux output.
	dw	diskst			;  5: disk read/write.
	dw	seekst			;  6: disk operation.


	; System messages.

signon	db	cr,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf,lf
	db	cr,lf,cr,lf,'Duplex 816 XIOS of 1-26-86',cr,lf
	db	'(c) 1986 Tarbell Electronics',cr,lf
	db	'Support for:',cr,lf
	db	'  ',,0		; error 2.
	db	'select:',0		; error 3.
drvmsg	db	' drive ',0
	db	', cylinder ',0
	db	', head ',0
	db	', sector ',0
	db	', status ',0

	; Local stack for disk i/o routines.
	rw	100			; 100 words for stack.
dskstk	equ	$
dskss	rw	1			; old stack segment.
dsksp	rw	1			; old stack pointer.

	; disk transfer parameters from concurrent stack.
mcnt	rb	1			; multi-sector count.
drive	rb	1			; drive number.
track	rw	1			; cylinder number.
sector	rw	1			; sector number.
dmaseg	rw	1			; transfer mber.
	db	drivel			; drive l number.
	db	drivem			; drive m number.
	db	driven			; drive n number.
	db	driveo			; drive o number.
	db	drivep			; drive p number.
;
;
curspt	rw	16		; current physical sectors/track.
curpsh	rb	16		; current physical sector shift factor.
oper	rb	1		; 0=seek, 1=read, 2=write disk operation.


	; Disk Parameter Header (DPH) address table.
	; these tables allow bdos to index the  drive attrib info tables.

dphtab	dw	(offset dph0)		; 5-inch floppy 0.
	dw	(offset dph

	if	nflop5 gt 2
	dw	0,0,0,0			; translate table, scratch.
	dw	f5dbds			; io_seldsk puts DPB address here.
	dw	0ffffh,0ffffh		; checksum, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif

	; 5-inch floppy unit 3.

dph3	equ	(offset $)
	if	nflop5 gt 3
	dw	0,0,0,0			; translate table, scratch.
	dw	f5dbds			; io_seldsk puts DPB address here.
	dw	0ffffh,0ffffh		; checksum, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif
	
	; - 8-inch ncrts+'0',' physical console'
	if ncrts gt 1! db 's'! endif
	db	cr,lf
	if	nvirt gt 1
	db	'  ',nvirt+'0',' total virtual consoles',cr,lf
	endif
	if	clock
	db	'  Clock Interrupt',cr,lf
	endif
	if	conint
	db	'  Console Input Interrupt',cr,lf
	endif
	if	dtrcon
	db	'  Console Output Handshaking',cr,lf
	endif
	if	nptrs gt 1
	db	'  ',nptrs+'0',' printers',cr,lf
	endif
	if	nflop5 gt 0
	db	'  ',nflop5+'0',' 5-inch diskettes',cr,lf
	endif
	if	nflop8 gt 0
	db	'  ',nflop8+'0',' 8-inch diskettes',csegment.
dmaoff	rw	1			; trnasfer offset.


	; disk control storage.

dens	db	0,0,0,0,0,0,0,0		; density info for 8 floppies.
diskno	dw	0			; current disk number and zero byte.
trk0	db	true			; track 0 Tarbell format flag.
trtab	db	0,0,0,0,0,0,0,0		; head position info for 8 floppies.
ercnt	db	0			; counter for r/w retrys.
sercnt	db	0			; counter for seek retrys.
clatch	db	0			; current code in latch.
iobyte	db	0			; system i/o redefinition byte.
msb20	db	0			; dma abs bits a16-a19.
lsb20	dw	1)		; 5-inch floppy 1.
	dw	(offset dph2)		; 5-inch floppy 2.
	dw	(offset dph3)		; 5-inch floppy 3.
	dw	(offset dph4)		; 8-inch floppy 0.
	dw	(offset dph5)		; 8-inch floppy 1.
	dw	(offset dph6)		; 8-inch floppy 2.
	dw	(offset dph7)		; 8-inch floppy 3.


	if nhard gt 0! dw offset dph8! endif	; hard disk 0.
	if nhard gt 1! dw offset dph9! endif	; hard disk 1.
	if nhard gt 2! dw offset dph10! endif	; hard disk 2.
	if nhard gt 3! dw offset dph11! endif	; hard disk 3.
	if nhard gt 4! dw offset dph12!um, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif				; end condition (nflop>1_true).


	; - 8-inch floppy diskette - unit 2.

dph6	equ	(offset $)

	if	nflop8 gt 2		; start condition (nflop>2_true).
	dw	0,0,0,0			; translate table, scratch.
	dw	f8dbds			; io_seldsk puts DPB address here.
	dw	0ffffh,0ffffh		; checksum, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif				; end condition (nflop>2_true).


	; - 8-inch floppy diskette -te table address.
	dw	offset f5p8ds
	db	00h,00000000b		; default sd ss 128x18 codes.
	dw	offset xlt5		; translate table address.
	dw	offset f5sdss
	endif

	; 8-inch table of disk parameter block addresses.

dpbt8	equ	(offset $)

	if	nflop8 gt 0
	db	0e7h,00000010b		; Tarbell sd ds 128x26 codes.
	dw	0			; translate table address.
	dw	(offset f8sdds)
	db	0ddh,00000001b		; Tarbell dd ss 128x51 codes.
	dw	0			; translate table address.
	dw	(offset f8ddss)
	db	0dfh,00000011b		; Tarbell dd ds 128tended DPB.
	dw	2		; nfats
	dw	1		; nfatrecs
	dw	320		; nclstrs
	dw	512*1		; clsize
	dw	1		; fatadd
	dw	8		; sectors per track
	db	3		; cp/m block shift <not used>
	db	7		; cp/m block mask <not used>
	db	0		; cp/m extnt mask <not used>
	dw	159		; cp/m disk size in 1k blocks
	dw	63		; directory max
	db	0		; cp/m alloc0 <not used>
	db	0		; cp/m alloc1 <not used>
	dw	16		; check size
	dw	0		; offset
	db	2		; phys sec shift
	db	3		; phys sec mask

	; 5-inch PC-DOS 512 x 8 double density doubl	0		; cp/m alloc1 <not used>
	dw	16		; check size
	dw	0		; offset
	db	2		; phys sec shift
	db	3		; phys sec mask

	; 5-inch Tarbell 512 x 10 double density single sided floppy.

f5dbss	dw	10		; physical sectors per track.
	db	4		; block shift factor.
	db	15		; block mask.
	db	0		; null mask.
	dw	94		; disk size-1.
	dw	81		; directory max.
	db	11000000b	; alloc 0.
	db	0		; alloc 1.
	dw	32		; check size.
	dw	2		; track offset.
	db	2		; physical record shift.
	db	3		; physical record mask.
 unit 3.

dph7	equ	(offset $)

	if	nflop8 gt 3		; start condition (nflop>3_true).
	dw	0,0,0,0			; translate table, scratch.
	dw	f8dbds			; io_seldsk puts DPB address here.
	dw	0ffffh,0ffffh		; checksum, allocation vectors.
	dw	0ffffh,0ffffh,0ffffh	; DIRBCB, DATBCB, TBLSEG.
	endif				; end condition (nflop>3_true).


	; Disk Parameter Blocks (DPB's).
	; these tables define the drive physical attributes.

	; 5-inch table of disk parameter block addresses.
	; 6 bytes per entry:
	;	1 byte for cx51 codes.
	dw	0			; translate table address.
	dw	(offset f8ddds)
	db	0deh,00000101b		; Tarbell dd ss 512x16 codes.
	dw	0			; translate table address.
	dw	(offset f8dbss)
	db	0dch,00000111b		; Tarbell dd ds 512x16 codes.
	dw	0			; translate table address.
	dw	(offset f8dbds)
	db	00h,00000000b		; DR/IBM sd ss 128x26 codes.
	dw	offset xlt8		; translate table address.
	dw	(offset f8sdss)
	endif


	if	nflop5 gt 0		; 5-inch disk parameter blocks.

	; 5-inch dummy DPB for genccpm process only.

e sided floppy.

f5p8ds	dw	0ffffh		; DOS media - extended DPB.
	dw	2		; nfats
	dw	1		; nfatrecs
	dw	320		; nclstrs
	dw	512*2		; clsize
	dw	1		; fatadd
	dw	8		; sectors per track
	db	3		; cp/m block shift <not used>
	db	7		; cp/m block mask <not used>
	db	0		; cp/m extnt mask <not used>
	dw	320-1		; cp/m disk size in 1k blocks
	dw	111		; directory max
	db	0		; cp/m alloc0 <not used>
	db	0		; cp/m alloc1 <not used>
	dw	16		; check size
	dw	0		; offset
	db	2		; phys sec shift
	db	3		; phys s
	; 5-inch Tarbell 512 x 10 double density, double sided floppy.

f5dbds	dw	10		; physical sectors per track.
	db	5		; block shift factor.
	db	31		; block mask.
	db	0		; extent mask.
	dw	94		; disk size - 1.
	dw	81		; directory max.
	db	11000000b	; alloc 0.
	db	0		; alloc 1.
	dw	32		; check size.
	dw	2		; track offset.
	db	2		; physical record shift.
	db	3		; physical record mask.

	; 5-inch 128 x 18 single density, single sided floppy.

f5sdss	dw	18		; physical sectors per track.
	db	3		ode that is read from track 0
	;	1 byte for internal density/sides code
	;	1 word for translate table address (0 if none)
	;	1 word for disk parameter block address

dpbt5	equ	(offset $)

	if	nflop5 gt 0
	db	01,00001101b		; DR/IBM dd ss 8-sector codes.
	dw	0			; translate table address.
	dw	offset f5i8ss
	db	02,00001111b		; DR/IBM dd ds 8-sector codes.
	dw	0			; translate table address.
	dw	offset f5i8ds
	db	0deh,00000101b		; Tarbell dd ss 512x10 codes.
	dw	0			; translate table address.
	dw
f5sgen	dw	8
	db	3
	db	7
	db	0
	dw	157
	dw	255
	db	10000000b
	db	0
	dw	16
	dw	1
	db	2
	db	3

	; 5-inch DR/IBM 512 x 8 double density single sided floppy.

f5i8ss	dw	8		; physical sectors per track.
	db	3		; block shift factor.
	db	7		; block mask.
	db	0		; null mask.
	dw	155		; disk size - 1.
	dw	63		; directory max.
	db	11000000b	; alloc 0.
	db	0		; alloc 1.
	dw	16		; check size.
	dw	1		; track offset.
	db	2		; physical record shift.
	db	3		; physical record mask.

	; 5-inch DR/ec mask

	; 5-inch PC-DOS 512 x 9 double density sяngle sided floppy.

f5p9ss	dw	0ffffh		; DOS media - extended DPB.
	dw	2		; nfats
	dw	2		; nfatrecs
	dw	360		; nclstrs
	dw	512*1		; clsize
	dw	1		; fatadd
	dw	9		; sectors per track
	db	3		; cp/m block shift <not used>
	db	7		; cp/m block mask <not used>
	db	0		; cp/m extnt mask <not used>
	dw	179		; cp/m disk size in 1k blocks
	dw	63		; directory max
	db	0		; cp/m alloc0 <not used>
	db	0		; cp/m alloc1 <not used>
	dw	16		; check size
	dw	; block shift factor.
	db	7		; block mask.
	db	0		; null mask.
	dw	71		; disk size - 1.
	dw	63		; directory max.
	db	11000000b	; alloc 0.
	db	0		; alloc 1.
	dw	16		; check size.
	dw	3		; track offset.
	db	0		; physical record shift.
	db	0		; physical record mask.

	endif			; end of 5-inch disk parameter blocks.

	if	nflop8 gt 0		; 8-inch disk parameter blocks.

	; 8-inch single density, double sided floppy diskette.

f8sdds	dw	26		; physical sectors per track.
	db	0004		; block shift.
	d	offset f5dbss
	db	0dch,00000111b		; Tarbell dd ds 512x10 codes.
	dw	0			; translate table address.
	dw	offset f5dbds
	db	0fch,00010101b		; PC-DOS dd ss 9-sector codes.
	dw	0			; translate table address.
	dw	offset f5p9ss
	db	0fdh,00010111b		; PC-DOS dd ds 9-sector codes.
	dw	0			; translate table address.
	dw	offset f5p9ds
	db	0feh,00010101b		; PC-DOS dd ss 8-sector codes.
	dw	0			; translate table address.
	dw	offset f5p8ss
	db	0ffh,00010111b		; PC-DOS dd ds 8-sector codes.
	dw	0			; translaIBM 512 x 8 double density double sided floppy.

f5i8ds	dw	8		; physical sectors per cylinder.
	db	4		; block shift factor for 2k blocks.
	db	15		; block mask for 2k blocks.
	db	1		; null mask.
	dw	009dh		; disk size - 1.
	dw	63		; directory max.
	db	10000000b	; alloc 0.
	db	0		; alloc 1.
	dw	16		; check size.
	dw	1		; track offset.
	db	2		; physical record shift.
	db	3		; physical record mask.

	; 5-inch PC-DOS 512 x 8 double density single sided floppy.

f5p8ss	dw	0ffffh		; DOS media - ex0		; offset
	db	2		; phys sec shift
	db	3		; phys sec mask

	; 5-inch PC-DOS 512 x 9 double density double sided floppy.

f5p9ds	dw	0ffffh		; DOS media - extended DPB.
	dw	2		; nfats
	dw	2		; nfatrecs
	dw	360		; nclstrs
	dw	512*2		; clsize
	dw	1		; fatadd
	dw	9		; sectors per track
	db	3		; cp/m block shift <not used>
	db	7		; cp/m block mask <not used>
	db	0		; cp/m extnt mask <not used>
	dw	360-1		; cp/m disk size in 1k blocks
	dw	111		; directory max
	db	0		; cp/m alloc0 <not used>
	db	db	0192		; alloc0.
	db	0000		; alloc1.
	dw	0032		; check size.
	dw	0002		; number of system tracks.
	db	0		; physical record shift.
	db	0		; physical record mask.


	; 8-inch double density, double sided floppy diskette.

f8ddds	dw	51		; physical sectors per track.
	db	0005		; block shift.
	db	0031		; block mask.
	db	0000		; extnt mask.
	dw	0237		; disk size - 1.
	dw	0095		; directory max.
	db	0192		; alloc0.
	db	0000		; alloc1.
	dw	0024		; check size.
	dw	0002		; number of system tracksb	21,02,08,14,20,26
	db	06,12,18,24,04,10
	db	16,22
	endif


	; Screen Tables.

forgnd	db	0			; foreground console number.
	if	ncrts gt 1
	db	nvirt0
	endif
	if	ncrts gt 2
	db	nvirt0+nvirt1
	endif
	if	ncrts gt 3
	db	nvirt0+nvirt1+nvirt2
	endif
	if	ncrts gt 4
	db	nvirt0+nvirt1+nvirt2+nvirt3
	endif
	if	ncrts gt 5
	db	nvirt0+nvirt1+nvirt2+nvirt3+nvirt4
	endif
	if	ncrts gt 6
	db	nvirt0+nvirt1+nvirt2+nvirt3+nvirt4+nvirt5
	endif
	if	ncrts gt 7
	db	nvirt0+nvirt1+nvirt2+nvirt3+nvirt4+nvir gt 11
	dw	scbufB
	endif
	if	nvirt gt 12
	dw	scbufC
	endif
	if	nvirt gt 13
	dw	scbufD
	endif
	if	nvirt gt 14
	dw	scbufE
	endif
	if	nvirt gt 15
	dw	scbufF
	endif

	endif


	; Buffers.

chkbuf	rb	chksiz			; buffer to check disk density code.

	; SCREEN BUFFERS - one for each virtual console.

	if	vcsbuf			; if virtual console screen buffers.
scbuf0	rw	maxcol*maxrow		; screen buffer.
	if	nvirt gt 1
scbuf1	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 2
scbuf2	rw	maxcol*m position to put character.
	dw	cibuf0			; next position to get character.

	if	ncrts gt 1
	dw	offset cibuf1		; console 1 input buffer adr.
	dw	offset cibuf1+cibmax-1	; buffer max position.
	dw	cibuf1			; next position to put character.
	dw	cibuf1			; next position to get character.
	endif

	if	ncrts gt 2
	dw	offset cibuf2		; console 2 input buffer adr.
	dw	offset cibuf2+cibmax-1	; buffer max position.
	dw	cibuf2			; next position to put character.
	dw	cibuf2			; next position to get character.
	db	0		; physical record shift.
	db	0		; physical record mask.

	; 8-inch 512 x 16 single sided diskette.

f8dbss	dw	16		; physical sectors per track.
	db	0004		; block shift.
	db	0015		; block mask.
	db	0000		; extnt mask.
	dw	0299		; disk size - 1.
	dw	0127		; directory max.
	db	0192		; alloc0.
	db	0000		; alloc1.
	dw	0032		; check size.
	dw	0002		; number of system tracks.
	db	2		; physical record shift.
	db	3		; physical record mask.

	; 8-inch 512 x 16 double sided diskette.

f8dt5+nvirt6
	endif
curpos	rw	nvirt			; cursor position table.
vpcont	db	0			; virtual-to-physical console table.
	if nvirt0 gt 1! db 0! endif
	if nvirt0 gt 2! db 0! endif
	if nvirt0 gt 3! db 0! endif
	if	ncrts gt 1
	db	1
	if nvirt1 gt 1! db 1! endif
	if nvirt1 gt 2! db 1! endif
	if nvirt1 gt 3! db 1! endif
	endif
	if	ncrts gt 2
	db	2
	if nvirt2 gt 1! db 2! endif
	if nvirt2 gt 2! db 2! endif
	if nvirt2 gt 3! db 2! endif
	endif
	if	ncrts gt 3
	db	3
	if nvirt3 gt 1! db 3! endif
	if nvirt3 gaxrow		; screen buffer.
	endif
	if	nvirt gt 3
scbuf3	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 4
scbuf4	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 5
scbuf5	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 6
scbuf6	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 7
scbuf7	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 8
scbuf8	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 9
scbuf9	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt .
	endif

	if	ncrts gt 3
	dw	offset cibuf3		; console 3 input buffer adr.
	dw	offset cibuf3+cibmax-1	; buffer max position.
	dw	cibuf3			; next position to put character.
	dw	cibuf3			; next position to get character.
	endif

	if	ncrts gt 4
	dw	offset cibuf4		; console 4 input buffer adr.
	dw	offset cibuf4+cibmax-1	; buffer max position.
	dw	cibuf4			; next position to put character.
	dw	cibuf4			; next position to get character.
	endif

	if	ncrts gt 5
	dw	offset cibuf5		; console 5 input bds	dw	16		; physical sectors per track.
	db	0005		; block shift.
	db	0031		; block mask.
	db	0000		; extnt mask.
	dw	0303		; disk size - 1.
	dw	0169		; directory max.
	db	0192		; alloc0.
	db	0000		; alloc1.
	dw	42		; check size.
	dw	0002		; number of system tracks.
	db	2		; physical record shift.
	db	3		; physical record mask.

	; 8-inch single density, single sided floppy diskette.

f8sdss	dw	26		; physical sectors per track.
	db	0003		; block shift.
	db	0007		; block mask.
	db	0000		; et 2! db 3! endif
	if nvirt3 gt 3! db 3! endif
	endif
	if	ncrts gt 4
	db	4
	if nvirt4 gt 1! db 4! endif
	if nvirt4 gt 2! db 4! endif
	if nvirt4 gt 3! db 4! endif
	endif
	if	ncrts gt 5
	db	5
	if nvirt5 gt 1! db 5! endif
	if nvirt5 gt 2! db 5! endif
	if nvirt5 gt 3! db 5! endif
	endif
	if	ncrts gt 6
	db	6
	if nvirt6 gt 1! db 6! endif
	if nvirt6 gt 2! db 6! endif
	if nvirt6 gt 3! db 6! endif
	endif
	if	ncrts gt 7
	db	7
	if nvirt7 gt 1! db 7! endif
	if nvirt7 gt 2! db 7! endif
	if nvirt7gt 10
scbufA	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 11
scbufB	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 12
scbufC	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 13
scbufD	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 14
scbufE	rw	maxcol*maxrow		; screen buffer.
	endif
	if	nvirt gt 15
scbufF	rw	maxcol*maxrow		; screen buffer.
	endif

	endif

	; console input interrupt buffers.

	if	conint			; if console interrupts.

cibuf0	rb	cibmax			; cbuffer adr.
	dw	offset cibuf5+cibmax-1	; buffer max position.
	dw	cibuf5			; next position to put character.
	dw	cibuf5			; next position to get character.
	endif

	if	ncrts gt 6
	dw	offset cibuf6		; console 6 input buffer adr.
	dw	offset cibuf6+cibmax-1	; buffer max position.
	dw	cibuf6			; next position to put character.
	dw	cibuf6			; next position to get character.
	endif

	if	ncrts gt 7
	dw	offset cibuf7		; console 7 input buffer adr.
	dw	offset cibuf7+cibmax-1	; buffer max position.
	dxtnt mask.
	dw	0242		; disk size - 1.
	dw	0063		; directory max.
	db	0192		; alloc0.
	db	0000		; alloc1.
	dw	0016		; check size.
	dw	0002		; number of system tracks.
	db	0		; physical record shift.
	db	0		; physical record mask.

	endif			; end of 8-inch disk parameter blocks.


	; Sector translation tables.

	; 5-inch

	if	nflop5 gt 0
xlt5	db	1,4,7,10,13,16
	db	2,5,8,11,14,17
	db	3,6,9,12,15,18
	endif

	; 8-inch

	if	nflop8 gt 0
xlt8	db	01,07,13,19,25,05
	db	11,17,23,03,09,15
	d gt 3! db 7! endif
	endif

scbuft	equ	$

	if	vcsbuf			; if virtual console screen buffers.
	dw	scbuf0			; screen buffer address table.
	if	nvirt gt 1
	dw	scbuf1
	endif
	if	nvirt gt 2
	dw	scbuf2
	endif
	if	nvirt gt 3
	dw	scbuf3
	endif
	if	nvirt gt 4
	dw	scbuf4
	endif
	if	nvirt gt 5
	dw	scbuf5
	endif
	if	nvirt gt 6
	dw	scbuf6
	endif
	if	nvirt gt 7
	dw	scbuf7
	endif
	if	nvirt gt 8
	dw	scbuf8
	endif
	if	nvirt gt 9
	dw	scbuf9
	endif
	if	nvirt gt 10
	dw	scbufA
	endif
	if	nvirtonsole 0 input buffer.

	if	ncrts gt 1
cibuf1	rb	cibmax			; console 1 input buffer.
	endif

	if	ncrts gt 2
cibuf2	rb	cibmax			; console 2 input buffer.
	endif

	if	ncrts gt 3
cibuf3	rb	cibmax			; console 3 input buffer.
	endif

	if	ncrts gt 4
cibuf4	rb	cibmax			; console 4 input buffer.
	endif

	if	ncrts gt 5
cibuf5	rb	cibmax			; console 5 input buffer.
	endif

cibtab	dw	offset cibuf0		; console 0 input buffer adr.
	dw	offset cibuf0+cibmax-1	; buffer max position.
	dw	cibuf0			; nextnumber.
	; Third byte of each entry is input ready mask.
	; Fourth byte of each entry is output ready mask.

cnstbl	dw	consts		; console 0 status port.
	db	conrda,contbe	; console 0 status masks.
	dw	spbase+1	; console 1 status port.
	db	spimsk,spomsk	; console 1 status masks.
	dw	spbase+3	; console 2 status port.
	db	spimsk,spomsk	; console 2 status masks.
	dw	spbase+5	; console 3 status port.
	db	spimsk,spomsk	; console 3 status masks.
	dw	spbase+7	; console 4 status port.
	db	spimsk,spomsk	;outine.
stkbase	equ	(offset $)	; define stack base address.

	if	clock
	rw	32		; tick interrupt stack.
ticktos	rw	0		; top of stack.
	endif

	if	conint
	rw	32		; console input interrupt stack.
cistkb	rw	0		; stack base.
	endif

lastoff	equ	(offset $)	; last used area address.
tpaseg	equ	(lastoff+0400h+15) / 16
tpalen	equ	0800h - tpaseg	; compute start and length of main tpa.

	db	0		; fill to last for gencmd.

	; assign external address locations.

	dseg	0		; obtain absolute low memory.; Tarbell Duplex 816 BOOT Module for Concurrent CP/M-86.
; Will work for CP/M-86 also, but note it requires 128K minimum.
; Copyright (c) 1984, Tarbell Electronics
; Last changed 10-28-84 by Don Tarbell

	; logical equates
false	equ	0
true	equ	not false
dubsid	equ	false		; this disk double sided?
mini	equ	false		; true for 5-inch floppy disks.

	; memory addresses.
bootad	equ	200h		; address of this module.
lodseg	equ	1e00h		; segment to load the sectors.
lsb20	equ	lodseg shl 4	; lower 16 of 2,ax
	mov	sp,bootad+100h	; put stack above this module.

	; set up the 80186 dma controller.
	mov	dx,dmaspu0	; source upper port.
	out	dx,ax		; source upper port=0.
	mov	ax,msb20	; get upper 4 bits of 20-bit load address.
	mov	dx,dmadpu0	; destination upper.
	out	dx,ax		; upper 4 bits of abs adr.
	mov	ax,lsb20	; get lower 16 bits of 20-bit load address.
	mov	dx,dmadpl0	; destination lower.
	out	dx,ax		; lower 16 bits of abs adr.
	mov	ax,nbytes-t0bps	; get number of bytes to move.
	mov	dx,dmatc0	 console 4 status masks.
	dw	spbase+11	; console 5 status port.
	db	spimsk,spomsk	; console 5 status masks.


	; Console Data Port Address Table.

cndtbl	dw	condat		; console 0 data port.
	dw	spbase		; console 1 data port.
	dw	spbase+2	; console 2 data port.
	dw	spbase+4	; console 3 data port.
	dw	spbase+6	; console 4 data port.
	dw	spbase+10	; console 5 data port.

	; List status port and mask table.

lpstbl	dw	lptsts		; list device 0 status port.
	db	0,lpttbe	; list device 0 status mask.

	org	0		; for interrupt vector ini info.

int0_offset	rw	1	; interrupt offset address.
int0_segment	rw	1	; interrupt segment address.

	rw	2*(bdos_int-1)	; pad to the system entry vector.
;
	end
fset $)	; last used area address.
tpaseg	equ	(lastoff+0400h+15) / 16
tpalen	equ	0800h - tpaseg	; compute start and length of main tpa.

	db	0		; fill to last for gencmd.

	; assign external address locations.

	dseg	0		; obtain absolute low memory.0-bit load address.
msb20	equ	lodseg shr 12	; upper 4 of 20-bit load address.
nxtseg	equ	lodseg		; next segment to execute.

	; sector and byte counts.

	if	not mini	; if 8-inch floppy.
t0spt	equ	26		; track 0 sectors per track.
t1spt	equ	16		; track 1 sectors per track.
fsize	equ	0ch		; bits 2 & 3 high for 8-inch.
	endif

	if	mini		; if 5-inch floppy.
t0spt	equ	18		; track 0 sectors per track.
t1spt	equ	10		; track 1 sectors per track.
fsize	equ	00h		; bits 2 & 3 low for latch.
	endif

t0; transfer count.
	out	dx,ax
	mov	ax,fdmard	; dma command.
	mov	dx,dmacon0	; dma control port.
	out	dx,ax		; arm the dma.

	; set up 2793 floppy controller.
	mov	dx,fcont	; get control register port.
	mov	al,10h+fsize	; get single density code for latch.
	out	dx,al		; do it.
	mov	bh,2		; init track count = 2.
	mov	bl,t0spt+1	; track 0 last sector + 1.
	mov	al,2		; set starting sector = 2.
rdtrk:	mov	dx,fsect	; get sector port.
	out	dx,al		; write al to sector port.
	mov	al,94h		; read multipl
	dw	spbase+7	; list device 1 status port.
	db	0,spomsk	; list device 1 status mask.
	dw	spbase+15	; list device 2 status port.
	db	0,spomsk	; list device 2 status mask.
	dw	spbase+11	; list device 3 status port.
	db	0,spomsk	; list device 3 status mask.
	dw	spbase+5	; list device 4 status mask.
	db	0,spomsk	; list device 4 status mask.


	; List device data port table.

lpdtbl	dw	lptdat		; list device 0 data port.
	dw	spbase+6	; list device 1 data port.
	dw	spbase+14	; list device 2 data portееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееbps	equ	128		; track 0 bytes per sector.
t1bps	equ	512		; track 1 bytes per sector.
t0bpt	equ	t0spt * t0bps	; track 0 bytes per track.
t1bpt	equ	t1spt * t1bps	; track 1 bytes per track.
nbytes	equ	t0bpt + t1bpt	; total bytes on system tracks.

	; 2793 floppy interface port addresses.
pcsbas	equ	0f000h		; peripheral register base adr.
fbase	equ	pcsbas + 80h	; 2793 floppy ic base address.
fdisk	equ	fbase		; command/status port.
fsect	equ	fbase + 4	; sector port.
fcont	equ	pcsbas + 100h	; control poe sectors.
	mov	dx,fdisk	; get command port number.
	out	dx,al		; commence multi-sector read.
	call	delay		; fool around a little.

	; wait for track completion.
sectlp:	mov	dx,fsect	; get sector port address.
	in	al,dx		; read sector number.
	cmp	al,bl		; is it past last one yet?
	jnz	sectlp		; keep checking if not.

	; terminate multi-sector read operation.
	mov	al,0d0h		; code to force interrupt.
	mov	dx,fdisk	; command port address.
	out	dx,al		; force interrupt.
	call	delay		; wait for g.
	dw	spbase+10	; list device 3 data port.
	dw	spbase+2	; list device 4 data port.


dispatch	rw	2	; entry address of dispatcher.
intssreg	rw	1	; stack segment of calling routine.
intspreg	rw	1	; stack pointer of calling routine.

	; SID's interrupt vectors are stored here during init.
vec1_off	dw	0	; interrupt vector 1.
vec1_seg	dw	0
vec3_off	dw	0	; interrupt vector 3.
vec3_seg	dw	0
vece1_off	dw	0	; interrupt vector e1.
vece1_seg	dw	0

	; Local Stacks.
	rw	32		; stack for initialization rееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееrt.

	; 80186 dma port addresses.
conbas	equ	0ff00h		; control block base after reset.
dmacon0	equ	conbas+0cah	; control word.
dmatc0	equ	conbas+0c8h	; transfer count.
dmadpu0	equ	conbas+0c6h	; destination pointer upper.
dmadpl0	equ	conbas+0c4h	; destination pointer lower.
dmaspu0	equ	conbas+0c2h	; source pointer upper.
dmaspl0	equ	conbas+0c0h	; source pointer lower.
fdmard	equ	0a266h		; dma floppy to memory code.

	cseg
	org	bootad

	xor	ax,ax		; clear segment registers.
	mov	ds,ax
	mov	ssd	al,80h		; is it still busy stepping?
	jnz	steplp		; loop back if so.
	endif

	if dubsid		; if double-sided disk.
	mov	al,40h+fsize	; get side-one latch code.
	mov	dx,fcont	; get control reg port adr.
	out	dx,al		; flip to other side.
	endif

	; prepare to read next track.
	mov	bl,t1spt+1	; get last sector + 1.
	mov	al,1		; get first sector number.
	jmps	rdtrk		; loop back and read track.

	; Provide some delay for status valid, etc.

delay:	mov	cx,1000h	; initialize counter.
delayl:	loop; Tarbell CP/M-86 Bios for Duplex 816 Board
; Copyright (c) 1983, 1984 by Tarbell Electronics.
; Last changed 6-24-84 by Don Tarbell.

	; truth equates.

true	equ	-1		; value of true for assembler.
false	equ	not true	; value of false for assembler.

loader	equ	true		; true if loader bios / false if system bios.
mpmldr	equ	false		; true if MP/M-86 loader bios.
sizmem	equ	true		; true if size cp/m-86 for maximum memory.

chksiz	equ	128		; bytes/sector on track 0.
dual	equ	false		; true if perscint	equ	2		; fdc seek retry count.
pcsbas	equ	0f000h		; peripheral ports base address.

	; console port addresses and mask bytes.

cbase	equ	pcsbas+180h	; port base address.
condat	equ	cbase+06h	; data port.
consts	equ	cbase+02h	; status port.
contbe	equ	04h		; transmit buffer empty mask.
conrda	equ	01h		; receive data available mask.
conpos	equ	true		; true if positive logic.

	; printer port addresses and mask bytes.

lbase	equ	pcsbas+190h	; port base address.
lptdat	equ	lbase+06h	; data por/trk
hstblk	equ	hstsiz/128	;CP/M sects/host buff
;
secshf	equ	2		;log2(hstblk)
cpmspt	equ	hstblk * hstspt	;CP/M sectors/track
secmsk	equ	hstblk-1	;sector mask

	; Bdos constants on entry to write

wrall	equ	0		;write to allocated
wrdir	equ	1		;write to directory
wrual	equ	2		;write to unallocated

	; define address refs for system or loader.

bdos_int equ	224		; reserved bdos interrupt.

	if	not loader	; start condition (loader_false).
bios_code	equ	2500h	; offset to start of bios within s	delayl		; decrement until zero.
	ret

	; Define the density selection byte.

	org	bootad+7dh

	if not dubsid		; if not double-sided.
	db	not(0deh), 0deh
	endif

	if dubsid		; if double-sided.
	db	not(0dch), 0dch
	endif

	; Define entry point of secondary loader.

	cseg	nxtseg
	org	0

entry:

	end
 back and read track.

	; Provide some delay for status valid, etc.

delay:	mov	cx,1000h	; initialize counter.
delayl:	loop drives.

	; Define number and kind of disk drives on system.

nflop8	equ	2		; number of 8-inch floppy drives.
nflop5	equ	0		; number of 5-inch floppy drives.
nhard	equ	0		; number of hard disk drives.
mcmi19	equ	false		; true for Morrow and CMI-19 hard disk.
mq540	equ	false		; true for Morrow and Quantum Q540.

	; define which drives are 8-inch and which are 5-inch.
	; 5-inch floppy drives are numbered 0-3, 8-inch from 4-7.
	; Hard disk drives are numbered from 8-0feh.
	; Undefined drive lettet.
lptsts	equ	lbase+02h	; status port.
lptcom	equ	lbase+04h	; command port.
lptinp	equ	lbase+0ah	; input port (for both channels).
lptdsr	equ	40h		; bit 6 of lptdat = 0 for dsr ready.
lpttbe	equ	04h		; transmit buffer empty mask.
lptrda	equ	01h		; receive data available mask.
lbaud	equ	0bh		; Baud Rate:  b=9600, c=19200.

	; Floppy disk controller port addresses.

fbase	equ	pcsbas+80h	; 2793 base address.
fdisk	equ	fbase		; command/status port.
ftrk	equ	fbase+2		; track port.
fsect	equ	fbase+4egment.
ccp_offset	equ	0000h	; offset to base of cp/m within segment.
bdos_ofst	equ	0b06h	; offset to bdos entry point within segment.
	endif			; end condition (loader_false).

	if	loader		; start condition (loader_true).
bios_code	equ	1200h	; offset to start of bios within segment.
	if	not mpmldr	; if not mp/m loader.
ccp_offset	equ	0003h	; offset to base of cp/m within segment.
	endif
	if	mpmldr		; if mp/m loader.
ccp_offset	equ	0103h	; offset to base of mp/m within segment.
	endif
bdos_ofst	ееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееееrs are numbered 0ffh.

drivea	equ	4		; drive a is 8-inch drive 0.
driveb	equ	5		; drive b is 8-inch drive 1.
drivec	equ	0		; drive c is 5-inch drive 0.
drived	equ	1		; drive d is 5-inch drive 1.
drivee	equ	8		; drive e is hard disk.
drivef	equ	0ffh		; drive f is undefined.
driveg	equ	0ffh		; drive g is undefined.
driveh	equ	0ffh		; drive h is undefined.
drivei	equ	0ffh		; drive i is undefined.
drivej	equ	0ffh		; drive j is undefined.
drivek	equ	0ffh		; drive k is undefined.
drivel	equ	0ffh		; d		; sector port.
fdata	equ	fbase+6		; data port.
fcont	equ	pcsbas+100h	; control port.

	; Floppy DMA port addresses and command words.

dmabas	equ	pcsbas+0fc0h	; dma controller base adr.
dmacon0	equ	dmabas+0ah	; control port.
dmatc0	equ	dmabas+08h