Actually working version of CP/M

Signed-off-by: H. Peter Anvin <hpa@zytor.com>

3 files changed, 92 insertions, 109 deletions

diff --git a/data/cbios.asm b/data/cbios.asm
index caaa382..77746ae 100644
--- a/data/cbios.asm
+++ b/data/cbios.asm
@@ -1,15 +1,15 @@
 ; SOCZ80 CP/M 2.2 BIOS (or at least an attempt!)
 ; 2013-11-03 Will Sowerbutts
-
+; 2014-06-01 H. Peter Anvin
+;
 ; useful resources:
 ;  http://www.cpm.z80.de/manuals/cpm22-m.pdf
 ;  http://www.retrotechnology.com/dri/howto_cpm.html#myown
 ;  http://www.retrotechnology.com/dri/cpm_features.html
 ;  cpmtools package
 
-msize:   	equ 64 			; KB of system RAM
-biosextra:	equ 512
-bias:    	equ (msize-20)*1024-biosextra
+msize:   	equ 63 			; KB of system RAM
+bias:    	equ (msize-20)*1024
 ccp:     	equ 0x3400+bias
 bdos:    	equ ccp+0x0806
 bios:    	equ ccp+0x1600
@@ -46,68 +46,37 @@ wboote:		jp wboot	; warm start
 kbdvec:		defw irq_kbd
 v24vec:		defw irq_v24
 	
-; disk parameter header (16 bytes for each drive), see page 6-28 in CP/M 2.2 operating system manual
+; disk parameter header (16 bytes for each drive),
+; the chk and alv get dynamically adjusted
 dpbase:
-            ; disk 0 (A)
-            dw 0            ; sector translation table (0 = no translation)
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw dirbf        ; DIRBUF (address of shared 128 byte scratch pad area)
-            dw dpblk        ; DPB (disk parameter block)
-            dw chk00        ; CSV (unique scratch pad used to check for changed disks)
-            dw alv00        ; ALV (unique scratch pad for allocation information)
-            ; end of disk 0
-
-            ; disk 1 (B)
-            dw 0            ; sector translation table (0 = no translation)
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw dirbf        ; DIRBUF (address of shared 128 byte scratch pad area)
-            dw dpblk        ; DPB (disk parameter block)
-            dw chk01        ; CSV (unique scratch pad used to check for changed disks)
-            dw alv01        ; ALV (unique scratch pad for allocation information)
-            ; end of disk 1
-
-            ; disk 2 (C)
-            dw 0            ; sector translation table (0 = no translation)
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw dirbf        ; DIRBUF (address of shared 128 byte scratch pad area)
-            dw dpblk        ; DPB (disk parameter block)
-            dw chk02        ; CSV (unique scratch pad used to check for changed disks)
-            dw alv02        ; ALV (unique scratch pad for allocation information)
-            ; end of disk 2
-
-            ; disk 3 (D)
-            dw 0            ; sector translation table (0 = no translation)
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw 0            ; must be 0
-            dw dirbf        ; DIRBUF (address of shared 128 byte scratch pad area)
-            dw dpblk        ; DPB (disk parameter block)
-            dw chk03        ; CSV (unique scratch pad used to check for changed disks)
-            dw alv03        ; ALV (unique scratch pad for allocation information)
-            ; end of disk 3
-
-ndisks:     equ 4           ; number of disks we defined
+		dw 0            ; sector translation table (0 = no translation)
+		dw 0            ; must be 0
+		dw 0            ; must be 0
+		dw 0            ; must be 0
+		dw dirbf        ; DIRBUF (address of shared 128 byte scratch pad area)
+		dw dpblk        ; DPB (disk parameter block)
+dp_csv:		dw csv          ; CSV (unique scratch pad used to check for changed disks)
+dp_alv:		dw alv          ; ALV (unique scratch pad for allocation information)
+
+ndisks:     equ 8           ; number of disks we defined
 
 ; disk parameter block (can be shared by all disks with same configuration)
-; each volue is 15,597,568 bytes (238*256*256).  We represent this as
+; each volue is 15,597,568 bytes (238*256*256), which is too much for
+; CP/M 2.2 to handle, so split each into two subvolumes.  We represent this as	
 ; tracks of 8192 bytes (64 sectors x 128 bytes) which matches an UFD-DOS
-; "cluster".  This means there are 1904 tracks.  The first track is reserved
-; for the system, leaving 1903*64 = 121792 user sectors.
-; We use 8K blocks, matching ABC clusters, so there are 1903 user blocks.
+; "cluster".  This means there are 952 tracks per subvolume.
+; The first track is reserved for the system, leaving
+; 951*64 = 60864 user sectors.  We use 8K blocks, matching ABC clusters,
+; so there are 951 user blocks.  A smaller block size eats up too much
+; memory in the alv tables.
 dpblk:
             dw 64           ; SPT: number of 128 byte sectors per track
             db 6            ; BSH: block shift factor (see manual for table)
             db 63           ; BLM: block mask (see manual for table)
             db 3            ; EXM: extent mask (see manual for table, using entries marked N/A turns out to be a bad idea!)
-            dw 1903         ; DSM: (disk bytes / block bytes) - 1, change alv0x etc if you change this; this is the number of the last sector on the disk, excluding system tracks (ie more system tracks -> this gets smaller)
-            dw 1023         ; DRM: directory max entries - 1
-            db 0xf0         ; AL0: directory sector allocation bitmask byte 0
+            dw 950          ; DSM: (disk bytes / block bytes) - 1, change alv0x etc if you change this; this is the number of the last sector on the disk, excluding system tracks (ie more system tracks -> this gets smaller)
+            dw 511          ; DRM: directory max entries - 1
+            db 0xc0         ; AL0: directory sector allocation bitmask byte 0
             db 0x00         ; AL1: directory sector allocation bitmask byte 1
             dw 0            ; CKS: check size (change chk0x etc if you change this)
             dw 1            ; OFF: track offset (number of system tracks)
@@ -153,12 +122,16 @@ boot:		; Cold boot
 		out (7),a	; Map 3, NMI disabled
             	ld sp,0x100	; Put our stack in the default DMA buffer
 
-		; Zero all memory (just in case)
-		ld hl,0
-		ld de,1
-		ld bc,bios-1
-		ld (hl),l
+		; Zero all memory (just in case).  This intentionally
+		; wraps around the end of memory.
+		ld ix,(currow)
+		xor a
+		ld hl,zero
+		ld de,zero+1
+		ld bc,bios-zero-1
+		ld (hl),a
 		ldir
+		ld (currow),ix
 
 		; say hello
 		ld hl,bootmsg
@@ -293,6 +266,7 @@ conout:		; write chracter from C to console
 		jr z,con_cr
 		; Fall through
 con_print:
+		and 07Fh
 		call con_getaddr
 		di
 		ld a,4			; Map 0, NMI off
@@ -443,17 +417,24 @@ seldsk:		; select disk indicated by register C
             	ld a, c
             	cp ndisks
             	ret nc      ; return (with error code) if C >= ndisks ie illegal drive
-            	ld (curdisk), a ; store current disk
+		or 24h*2	; +4 for volume, CP/M mode, C flag <- 0
+		rra
+		ld (curdisk), a ; store current ABC volume number + CP/M flag
+		ld a,h		; H = 0!
+		jr nc,sd1
+		ld a,119
+sd1:		ld (curxtrk), a	; store track offset (+119 for odd volume)
             	; compute proper disk parameter header address in HL
-		add a,a		; *2
-		add a,a		; *4
-		add a,a		; *8
-		add a,a		; *16
-		add a,dpbase & 0xff
-		ld l,a
-		ld h,dpbase/256
-		; HL = dpbase + disk number * 16
-            	ret
+
+		; Each allocation vector is 120 bytes long
+		ld a,120
+		ld e,c
+		ld d,h		; = 0
+		ld hl,alv
+		call multiply_add
+		ld (dp_alv),hl
+		ld hl,dpbase
+		ret
 
 home:		ld bc, 0
 		; fall through into seltrk
@@ -477,24 +458,26 @@ setdma:		; set DMA address given by BC
 		ret
 
 read:		; read a sector from disk
-		; XXX: add error handing!
+		; XXX: add error handing before trying to read back data
 		ld c,03h		; READ + SECTOR TO HOST
 		call sendcmd
 		ld hl,(curdmaaddr)
 		ld bc,128*256+0
 		inir
-		xor a			; Success!
+end_op:
+		in a,(1)
+		rrca
+		jr nc,end_op
+		in a,(0)		; 0 = OK
 		ret
 
 write:		; write sector to disk
-		; XXX: add error handing!
 		ld c,0Ch		; SECTOR FROM HOST + WRITE
 		call sendcmd
 		ld hl,(curdmaaddr)
 		ld bc,128*256+0
 		otir
-		xor a			; Success!
-		ret
+		jr end_op
 
 		; Send a controller command, C = K0 command byte
 		; Clobbers A DE HL, returns with disk selected
@@ -503,8 +486,7 @@ sendcmd:
 		out (1),a		; Select disk
 		out (2),a		; Start command
 
-		ld a,(curdisk)		; curdisk
-		or 24h			; +4 for volume, CP/M mode
+		ld a,(curdisk)		; curdisk + 24h
 		ld e,a
 		ld a,(cursector)
 		srl a
@@ -524,6 +506,9 @@ bc1:
 		rr d
 		or d
 		ld h,a
+		ld a,(curxtrk)
+		add a,l
+		ld l,a
 
 		; Now: K0 = C, K1 = E, K2 = L, K3 = H
 sc_wait1:
@@ -547,26 +532,34 @@ sc_wait_ok:
 		ret c
 		jr sc_wait_ok
 
-bootmsg:	db "CP/M BIOS (H. Peter Anvin, 2014-05-09)\r\n"
+multiply_add:	; HL <- HL + DE * A, trashes B
+		ld b,8
+m1:
+		rrca
+		jr nc,m2
+		add hl,de
+m2:
+		sla e
+		rl d
+		djnz m1
+		ret
+
+bootmsg:	db "CP/M BIOS (H. Peter Anvin, 2014-06-01)\r\n"
 		db "CP/M 2.2 Copyright 1979 (c) by Digital Research\r\n"
+zero:
 		db 0
 
-;---------------------------------------------------------------------------------------------------------------
+; ----------------------------------------------------------------------------
 
-; scratch RAM used by BIOS
-curdisk:    db 0
-cursector:  db 0
-curtrack:   dw 0
-curdmaaddr: dw 0
-conflag:    db 0
+; scratch RAM (BSS) used by BIOS
+curdisk:	db 0
+curxtrk:	db 0
+cursector:	db 0
+curtrack:	dw 0
+curdmaaddr:	dw 0
+conflag:	db 0
 
 ; scratch RAM used by BDOS
 dirbf:      ds 128           ; directory scratch area
-alv00:      ds 239           ; allocation vector for disk 0, must be (DSM/8)+1 byte
-alv01:      ds 239           ; allocation vector for disk 1, must be (DSM/8)+1 bytes
-alv02:      ds 239           ; allocation vector for disk 2, must be (DSM/8)+1 bytes
-alv03:      ds 239           ; allocation vector for disk 3, must be (DSM/8)+1 bytes
-chk00:      ds 0             ; check vector for disk 0 (must be CKS bytes long)
-chk01:      ds 0             ; check vector for disk 1 (must be CKS bytes long)
-chk02:      ds 0             ; check vector for disk 2 (must be CKS bytes long)
-chk03:      ds 0             ; check vector for disk 3 (must be CKS bytes long)
+alv:        ds 120*ndisks    ; allocation vectors, each (DSM/8)+1 byte
+csv:        ds 0*ndisks      ; check vectors, each CKS bytes
diff --git a/data/cpm.asm b/data/cpm.asm
index 061a3c3..0e7bdbd 100644
--- a/data/cpm.asm
+++ b/data/cpm.asm
@@ -14,8 +14,8 @@
 ; CP/M loader for ABC80-DE1
 ;
 HDSEL:		equ 36
-RAMSIZE:	equ 64
-BIAS:		equ (64-20)*1024-512
+RAMSIZE:	equ 63
+BIAS:		equ (RAMSIZE-20)*1024
 CPMBIOS:	equ BIAS+4A00h
 ABCCURSOR:	equ 65011
 CPMCURSOR:	equ 0FFFEh
@@ -36,15 +36,6 @@ _start:
 		ld bc,bios_size
 		ldir
 
-		; Zero memory above the BIOS
-		ld l,e
-		ld h,d
-		inc de
-		ld bc,CPMCURSOR-(CPMBIOS+bios_size)-1
-		xor a
-		ld (hl),a
-		ldir
-
 		jp CPMBIOS
 
 bios:
diff --git a/data/cpm22.asm b/data/cpm22.asm
index 039dc59..90b6c96 100644
--- a/data/cpm22.asm
+++ b/data/cpm22.asm
@@ -11,8 +11,7 @@
 ;   Set memory limit here. This is the amount of contigeous
 ; ram starting from 0000. CP/M will reside at the end of this space.
 ;
-MEM:	EQU	64		;for a 64k system (TS802 TEST - WORKS OK).
-XBIOS:	EQU	512		;extra space for BIOS
+MEM:	EQU	63		;for a 64k system (TS802 TEST - WORKS OK).
 ;
 IOBYTE:	EQU	3		;i/o definition byte.
 TDRIVE:	EQU	4		;current drive name and user number.
@@ -40,7 +39,7 @@ DEL:	EQU	7FH		;rubout
 ;
 ;   Set origin for CP/M
 ;
-	ORG	(MEM-7)*1024-XBIOS
+	ORG	(MEM-7)*1024
 ;
 CBASE:	JP	COMMAND		;execute command processor (ccp).
 	JP	CLEARBUF	;entry to empty input buffer before starting ccp.