;******************************************************
;* CUSTOM BIOS FOR CP/M 2.2, STOLEN FROM FERGUSEN     *
;* BIG BOARD. MODIFIED FOR XEROX 820 USING SAMPLE     *
;* BIOS FROM DIGITAL RESEARCH.(ASM85)	   	      *
;******************************************************
;
; Mark Richey 		11-March-1986
;
; *** Modified to support modem control SIOB ***
;
;
msize 	equ	60		;mem in kbytes
monitr	equ	0f000h		;monitor residence     
baud    equ	0ch		;channel b baud rate generator
;
;	cpm constants
;
bias	equ	(msize-20)*1024
ccp	equ	3400h+bias
bdos	equ	ccp+806h
cbios	equ	ccp+1600h
cdisk	equ	04h
iobyte	equ	03h
;
	org	cbios
;
	jmp	boot		;jump table for xerox 820 
bvectr:	jmp	wboot		;custom bios subroutines
svectr:	jmp	const
ivectr:	jmp	conin
ovectr:	jmp	conout
lvectr:	jmp	lstout		;list device vector
	jmp 	conout  	;punch not configured
	jmp	modmin		;reader device vector (tty input)
	jmp 	home
	jmp	select	
	jmp	seek
	jmp	setsel
	jmp	setptr
	jmp	read
	jmp	write
	jmp	lstst		;list device status
	jmp	trans
;
;
boot:	xra	a
	sta	iobyte		;reset io byte to 0
	sta	cdisk
	lxi	signon
	call	pmsg		;print signon message
	jmp	gocpm
;
;
wboot:	lxi	sp,stack
	mvi	c,0
	call	select		;select unit a
	call	home		;seek track 0
	lxi	h,3400h+bias
Š	mvi	b,0d02h
	call	rdloop		;read even sectors	
	lxi	h,3480h+bias
	mvi	b,0c03h
    	call	rdloop		;read odd sectors
	mvi	c,1
    	call	seek		;seek track 1
	jnz	bomb
	lxi	h,4080h+bias
	mvi	b,0a01h
	call	rdloop		;read odd sectors
	lxi	h,4100h+bias
	mvi	b,0902h
	call	rdloop		;read even sectors on 1
gocpm:	mvi	a,0c3h		;store jump vectors
	sta	(00h)
	lxi	h,cbios+3	;jump to warm boot @ 0
	shld	(01H)
	sta	(05H)
	lxi	h,bdos		;jump to bdos at 5h
	shld	(06H)
   	sta	(38H)
	lxi	h,monitr	;jump to monitor at 38h
	shld	(39H)
   	mvi	b,0080h
	call	setptr		;disk buffer = 80h
	mvi	c,0
	jmp	ccp
;
;
rdloop:	shld	(pointr)	;store adr from hl
	mov	a,c
	sta	(sector)	;store sector from c
	push	 h
	push	 b	
	call 	read
	pop	b
	pop	h
	jnz	bomb
	inr	h		;add 256 to load adress
	inr	c
	inr	c		;add 2 sectors
	dcr	b
	jnz	rdloop
	ret
;
;
bomb:	lxi	h,dead
	call	pmsg
loop:	jmp	loop
;
dead:	db	cr,lf
	dm	'cannot boot cp/m $'
;
;
const:	jmp 	monitr+6	;monitor console status return
;
Šconin:	jmp	monitr+9	;monmitor console input return
;
conout:	mov	a,c    
	jmp	monitr+12	;monitor console output return
;
lstout:	mov	a,c
	jmp	monitr+15	;monitor ptr (sio) return
;
lstst:	jmp	monitr+18	;monitor list status return
;
modmin:	jmp	monitr+21	;monitor siob input return
;
;
;
;*** DISK I/O SUBROUTINES ****
;
;
;Sector translation for 1 in 6 interleave.
;
;
sectab:	db	1,7,13,19
	db	25,5,11,17
	db	23,3,9,15
	db	21,2,8,14
	db	20,26,6,12
	db	18,24,4,10
	db	16,22
;
; 
;   Disk Parameter Block for 8" Floppy
;
dpblk:	dw	26		;sectors per trk
	db	3		;block shift constant
	db	7		;block mask
	db	0		;extent mask
	dw	242		;max block
	dw	63		;max dir
	db	11000000b	;msb	allocation
	db	00000000b	;lsb	allocation
	dw	16		;check size
	dw	2		;reserved trks
;
;
;	Disk param headers for 4 disks
;
;
dphtab:	dw	sectab,000h		;unit 0,a
	dw	000h,000h
	dw	dirbuf,dpblk
	dw	chk0,all0

	dw	sectab,0000h	;unit 1,b
	dw      0000h,0000h
	dw      dirbuf,dpblk
	dw	chk1,all1

	dw	sectab,000h	;unit 2,c
	dw	000h,000h
	dw	dirbuf,dpblk
	dw	chk2,all2

	dw	sectab,000h	;unit 3,d
	dw	0000h,0000h
	dw	dirbuf,dpblk
	dw	chk3,all3
;
;
;
setsec:	mov	a,c
	sta	(sector)	;store sector number from b
	ret
;	
;
trans:	xchg	d,h		;add translation table address
	dad	b		;passed in d to sector in b
	mov	l,(h)
	mvi	h,0		;find physical sector
	ret			;and return in h
;
;
setptr:	mov	l,c	 	;low order address
	mov	l,m		;hi order address
	shld	(pointr)	;save the address
						
select:	lxi	h,0	 	;error return code
	mov	a,c
	cpi	4
	rnc			;retr with hl=0 if c>3
	sta	(unit)		;store c as new drive #
	mov	l,a
	dad	h
	dad	h
	dad	h
	dad	h		;mult unit by 4
	lxi	d,dphtab
	dad	d		;add start
	push	h
	mov	c,a		;load drive number
	mvi	b,0		;load seek speed
	call	monitr+27
	pop	h
	rz			;exit if successful
	pop	h	
	mvi	c,l
	call	report	
	jnz	sel2		;jump if abort
	lda	(unit)		;else try again
	mov	c,a
	jmp	select

sel2:	mvi	h,0		;disable bdos calls
	ret
;
;
;
home:	call 	monitr+30	;home routine in monitor
	rz			;back if all ok
	mvi	c,2		
	call	report	
	jz	home		;try again if no one home
	ret	
;	
;	
;	
seek:	mov	a,c		;get track number
	sta	(track)
	call	monitr+33	;seek routine in monitor
	rz			;leave if ok
	mvi	c,2
	call 	report		;tell console about it
	rnz			;return permanent error
	lda	(track)		;unless retry indicated
	mov	c,a
	jmp	seek
;
;
read:	lhld	(pointr)
	lda	(sector)
	mov	c,a
	call	monitr+36	;read routine in monitor
	rz			;back if oki doki
	mov	c,3		;tell bdos about it
	call 	report		;console wants to know too
	jz	read		;try again?
	ret
;
;
write:	lhld	(pointr)
	lda	(sector)
	mov	c,a
	call	monitr+39	;write routine in monitor
	rz			;see read, same line
	mov	c,4		;bdos again!
	call	report		;console same
	jz	write		;try again?
	ret
;
;
report:	sta	(flags)		;1771 i/o status
	mov	a,c
	sta	(class)		;command error class
	lxi	h,dskmsg
	call 	pmsg		;start message printout
	dcx	h
	lda	(class)
	mov	b,a
rep1:	call	skip		;skip to next $
	dcr	b		
	jnz	rep1
	call	pmsg		;print new string
	lxi	h,errmsg
	call    pmsg		;print 'error' after type
	lda	(flags)			 
	ral			;test for drive not ready
	jmp	rep8		;and jump if thats it
	cpi	3		;is it select/seek?
	jnc	rep2
	lxi	h,skerrs	;point to proper messages
rep2:	mvi	b,5
	mov	d,a		;reset bit 0
	ani	00000001b	
	mov	a,d
rep4:	
;
;
;
; start again here insert from rep4
;
;
;
lf	equ	0ah
cr	equ	0dh

dskmsg:	db	cr,lf
	dm	'bios $'
	dm	'select $'
	dm	'seek $'
	dm	'read $'
	dm	'write $'

errmsg:	dm	'error $'

skerrs:	dm	'$'
	dm	'$'
	dm	'cannot seek$'
	dm	'bad crc$'
	dm	'cannot restore$'

rdymsg:	dm	'drive not rdy-$'

rwerrs:	dm	'write protected$
	dm	'write fault$'
	dm	'record not found$'
	dm	'bad crc$'
	dm	'data overrun$'

tsmsg:	dm	'trk/sect = $'

signon:	db	cr,lf
	dm	'60k CP/M version 2.2'
	db	cr,lf
	dm	'custom version for xerox 820'
	db	cr,lf
	dm	'on line bullitin board---M.R. Apr. 86'
	db	cr,lf
	db	cr,lf
	dm	'channel B baud = 1200'
crlf:	db 	cr,lf
	db	'$'
;
;
unit:	ds	1
track:	ds	1
sector:	ds	1
pointr:	ds	1
flags:	ds	1
class:	ds	1
	ds	32
stack:	ds	1		;local stack for wboot
;
;
;***** Disk I/O buffers for bdos *****
;
;
dirbuf:	ds	128		;scratch directory
;
all0:	ds	32		;unit a allocation
chk0:	ds	16		;unit 0 check
all1:	ds	32
chk1:	ds	16
all2:	ds	32
chk2:	ds	16
all3:	ds	32
chk3:	ds	16
;
;
	db	1,baud
	db	00000111b	;1200 baud
;
	end