*****************************************************************
*								*
*	 Morrow Designs CP/M vers 2.2 Cold Boot Loader.		*
*		  Cbios revision E.2,  3/4/82.			*
*								*
* The following routines will boot CP/M from the		*
* Disk Jockey 2D Rev. B 8 inch disk controller (DJ2D/B),	*
*								*
*	     8 inch floppy disk boot loader for the		*
*            Morrow Designs Disk Jockey 2D/B (DJ2DB)		*
*								*
* The 'order' column is the interleave sequence used by the	*
* loader during the load.					*
*								*
*   track   sector    sysgen	load order	Name		*
*								*
*	0	 1	 900	ff00	 0	Boot loader	*
*	0	 2	 980			Unused		*
*	0	 3	 a00					*
*	0	 4	 a80					*
*	0	 5	 b00	9100	 1	CCP		*
*	0	 6	 b80	9180	12			*
*	0	 7	 c00	9200	 2			*
*	0	 8	 c80	9280	13			*
*	0	 9	 d00	9300	 3			*
*	0	10	 d80	9380	14			*
*	0	11	 e00	9400	 4			*
*	0	12	 e80	9480	15			*
*	0	13	 f00	9500	 5			*
*	0	14	 f80	9580	16			*
*	0	15	1000	9600	 6			*
*	0	16	1080	9680	17			*
*	0	17	1100	9700	 7			*
*	0	18	1180	9780	18			*
*	0	19	1200	9800	 8			*
*	0	20	1280	9880	19			*
*	0	21	1300	9900	 9	BDOS		*
*	0	22	1380	9980	20			*
*	0	23	1400	9a00	10			*
*	0	24	1480	9a80	21			*
*	0	25	1500	9b00	11			*
*	0	26	1580	9b80	22			*
*								*
* Track 1 is recorded in double density format.  There are	*
* 1024 bytes per sector.					*
*								*
*	1	 1	1600	9c00	 4			*
*	1	 2	1a00	a000	 1			*
*	1	 3	1e00	a400	 5	CBIOS (@ a700h)	*
*	1	 4	2200	a800	 2			*
*	1	 5	2600	ac00	 6			*
*	1	 6	2a00	b000	 3			*
*	1	 7	2e00	b400	 7			*
*	1	 8	3200	b800		Unused		*
*								*
* Three spare sectors (track 0, sectors 2 to 4) have been	*
* provided for a more advanced boot loader at a later date.	*
*								*
* The warm boot loader starts on track 0, sector 5 and		*
* continues through to track 1 sector 3.  Only the first	*
* 3/4 K bytes of track 1, sector 3 is loaded since CP/M		*
* requires that the warm boot loader load up to the start	*
* of (but not past) the Cbios jump table.			*
*								*
*****************************************************************

*****************************************************************
*								*
* The following table gives a general idea as to where the	*
* various parts of of the operating system are in memory.	*
*								*
* The only changes to the map that I see in the future is	*
* the increasing the space for the uninitialized tables		*
* following the Cbios.  The amount of code and table space	*
* that can actually be loaded from the disk is fixed by the	*
* amount of space available on the system tracks.		*
*								*
* Our most restrictive (smallest) drive is the 5 1/4 inch	*
* 'minnie floppy'.  This drive has 20 512 byte sectors for	*
* a total of 10k bytes on the system tracks.  The 8 inch	*
* floppy disk drive is also very close to being filled up.	*
*								*
* Since 512 bytes are reserved for the cold boot loader we	*
* have a total of 9.5k bytes for the operating system.  Out	*
* of this 5.5k bytes are used by the (CCP + BDOS) leaving	*
* us with a total of 4k bytes of loaded code and data space	*
* to play with.  Right now we are using all of this space	*
* so any major additions will have to result in a little	*
* (lot?) of code shuffeling or in the creation of a Cbios	*
* that simply will not fit on a small disk drive.		*
*								*
*	sysgen	48k	56k	60k	62k	64k		*
*	 image	CP/M	CP/M	CP/M	CP/M	CP/M		*
*								*
*	 900	~~~~	~~~~	~~~~	~~~~	~~~~	Loader	*
*	 b00	9500	b500	c500	cd00	d500	CCP	*
*	1300	9d00	bd00	cd00	d500	dd00	BDOS	*
*	2100	ab00	cb00	db00	e300	ed00	Cbios	*
*	3100	bb00	db00	eb00	f300	fb00	Tables	*
*	35ff	bfff	dfff	efff	f7ff	ffff	The End	*
*								*
*	~~~~	8d00	ad00	bd00	c500	cd00	DDT	*
*								*
*****************************************************************
	

msize	equ	56		;Memory size of target CP/M
			
biosln	equ	10h		;BIOS length
codlen	equ	11h		;Code length
	
ccpln	equ	800h
bdosln	equ	0e00h

size	equ	(msize*1024)	
ccp	equ	size-(biosln*100h+ccpln+bdosln)
bdos	equ	ccp+ccpln
bios	equ	ccp+ccpln+bdosln

cboot	equ	bios		;Cold boot address for CP/M
loaddr	equ	ccp		;Load address for floppy

retries	equ	10		;Maximum # of disk retries

*****************************************************************
*								*
* The following equates are for the Disk Jockey 2D/B.		*	
*								*
*****************************************************************

origin	equ	0E000H		;Orgin of DJ 2D Mod B PROM
djram	equ	origin+400h
				;Disk Jockey 2D Mod B routines
tkzero	equ	origin+9h	;Track 0 seek
trkset	equ	origin+0ch	;Set track
setsec	equ	origin+0fH	;Set sector
setdma	equ	origin+12h	;Set DMA address
dread	equ	origin+15h	;Read sector
dmast	equ	origin+24h	;Get DMA address
status	equ	origin+27h	;Disk status
dskerr	equ	origin+2ah	;Flash error light
setden	equ	origin+2dh	;Set density

boot	equ	djram+300h	;Upper 3/4 of on board floppy RAM
offset	equ	900h-boot	;DDT offset

	org	boot

*****************************************************************
*								*
* Cold boot loader for the Disk Jockey 2D Revision B controller	*
*								*
*****************************************************************

t0boot	mvi	a,5-2		;First sector - 2
newsec	equ	$-1
	inr	a		;Update sector #
	inr	a
	cpi	27		;Size of track in sectors + 1
trksiz	equ	$-1
	jc	nowrap		;Skip if not at end of track
	jnz	t1boot		;Done with this track
exit	equ	$-2
	sui	27-6		;Back up to sector 6
backup	equ	$-1
	lxi	h,loaddr-80h	;Memory address of sector - 100h
nxtdma	equ	$-2
	shld	newdma
nowrap	sta	newsec		;Save the updated sector #
	mov	c,a
	call	setsec		;Set up the sector
	lxi	h,loaddr-100h	;Memory address of sector - 100h
newdma	equ	$-2
	lxi	d,100h		;Update DMA address
secsiz	equ	$-2
	dad	d
nowrp	shld	newdma		;Save the updated DMA address
	mov	b,h
	mov	c,l
	call	setdma		;Set up the new DMA address
	lxi	b,retries*100h+0;Maximum # of errors, track #
nxtrty	equ	$-2
fread	push	b
	call	trkset		;Set up the proper track
	call	dread		;Read the sector
	pop	b
	jnc	t0boot		;Continue if no error
	dcr	b
	jnz	fread		;Keep trying if error
	jmp	dskerr		;Too many errors, flash the light

t1boot	lxi	h,cboot		;We jump to cboot next time
	shld	exit
	mvi	c,1		;Select double density
	call	setden
	xra	a		;First sector - 2
	sta	newsec
	mvi	a,8		;Size of (logical) track + 1
	sta	trksiz
	dcr	a		;Number of sectors to back up
	sta	backup
	lxi	h,loaddr+0700h	;DMA start address for first revolution - 2048
	shld	newdma
	lxi	h,loaddr+0300h	;DMA start address for second revolution - 2048
	shld	nxtdma
	lxi	h,2048		;Difference between DMA addresses
	shld	secsiz
	lxi	h,retries*100h+1;Maximum # of errors, track #
	shld	nxtrty
	jmp	t0boot		;Go load in track 1

	end