agp.cooperUpdated Boot
First I have to update boot.asm, the code to load CP/M into memory. The CP/M V2 only had 32kb of RAM so the CP/M source was located at 0x8000. As CP/M V3 has 56k of RAM so the CP/M source is located at 0xE000.
Here is the boot assembly code (i8085):
; boot.asm: Load CP/M from ROM
; Calc CPM addresses
msize equ 56 ; 56k RAM
sectors equ 16 ; sectors per track for my system
systrks equ 4 ; my boot system has 4 tracks of 16 sectors
bias equ (msize-20-1)*1024 ; calculation for my system
ccp equ 3400h+bias
cstart equ 4a00h+bias
org 0e000h ; executed in ROM after shift down
jmp 0e003h ; reset bootstrap
boot:
di ; disable interrupts
lxi sp,ccp-0080h ; convenient place
lxi d,ccp-0080h ; start of boot dst
lxi h,0e000h ; start of ROM (boot src)
mvi c,sectors ; sectors per track
mvi b,systrks ; sytem track count
push b ; save
boot$nextsect:
mvi b,128 ; sector size
boot$copysect:
mov a,m
inx h
stax d
inx d
dcr b
jnz boot$copysect
dcr c
jnz boot$nextsect
pop b
dcr b
push b
jnz boot$nextsect
; Cold boot
jmp cstart
end
Updated CBIOS
CBIOS has a number of alterations to suit the new hardware design:
; Calc CPM addresses
msize equ 56 ; RAM capacity
sectors equ 16 ; sectors per track for my system
systrks equ 4 ; my boot system has 4 tracks of 16 sectors
bias equ (msize-20-1)*1024 ; adjusted for my system
cbase equ 3400h+bias ; base of ccp
fbase equ cbase+800h ; base of bdos
bdos equ cbase+806h ; bdos entry
cbios equ cbase+1600h ; base of custom bios (cold boot entry)
spbase equ msize*1024 ; sp base (use top of RAM)
usrdsk equ 0004h ; current user and disk number
iobyte equ 0003h ; intel i/o byte
rst7.5 equ 003ch ; interrupt to read serial data input
lf equ 0ah ; line feed
cr equ 0dh ; carriage return
; Custom CP/M 2.2 BIOS
org cbios
; jump vector for individual subroutines
jmp cboot ; cold start
wstart:
jmp wboot ; warm start
jmp const ; console status
jmp conin ; console character in
jmp conout ; console character out
jmp list ; list character out
jmp punch ; punch character out
jmp reader ; reader character out
jmp home ; move head to home position
jmp seldsk ; select disk
jmp settrk ; set track number
jmp setsec ; set sector number
jmp setdma ; set dma address
jmp read ; read disk
jmp write ; write disk
jmp listst ; return list status
jmp sectran ; sector translate
; System uses a two Flash AT29C020-90B with 2048 x 128b pages (256k)
; Set as 128 tracks of 16 sectors of 128 bytes
; System uses tracks 0 to 3 (64 sectors)
; Directory is track 4 and 7 (128 entries)
; Leaving 240kb file storage using 2048b blocks per chip
dpbase:
; disk Parameter header for disk A (system)
dw trans, 0000h
dw 0000h, 0000h
dw dirbf, dpblk256s
dw chk00, all00
; disk parameter header for disk B (system)
dw trans, 0000h
dw 0000h, 0000h
dw dirbf, dpblk256s
dw chk01, all01;
; disk parameter header for disk C (data) - Not installed
dw trans, 0000h
dw 0000h, 0000h
dw dirbf, dpblk256d
dw chk02, all02
; disk parameter header for disk D (data) - Not installed
dw trans, 0000h
dw 0000h, 0000h
dw dirbf, dpblk256d
dw chk03, all03
; sector translate vector (i.e. no translation)
trans:
db 1, 2, 3, 4 ; sectors 1, 2, 3, 4
db 5, 6, 7, 8 ; sectors 5, 6, 7, 6
db 9, 10, 11, 12 ; sectors 9, 10, 11, 12
db 13, 14, 15, 16 ; sectors 13, 14, 15, 16
; disk parameter block for system disk (256k) and 1k block size
dpblk256s:
dw sectors ; SPT: sectors per track
db 3 ; BSH: block shift factor
db 7 ; BLM: block mask
db 0 ; EXM: extended block mask
dw 247 ; DSM: disk blocks - 1
dw 127 ; DRM: directory max - 1
db 240 ; AL0: alloc 0 (=4 bits)
db 0 ; AL1: alloc 1
dw 0 ; CKS: check size (= not removable)
dw systrks ; OFF: track offset
; disk parameter block for data disk (256k) and 1k block size
dpblk256d:
dw sectors ; SPT: sectors per track
db 3 ; BSH: block shift factor
db 7 ; BLM: block mask
db 0 ; EXM: extended block mask
dw 255 ; DSM: disk blocks - 1
dw 127 ; DRM: directory max - 1
db 240 ; AL0: alloc 0 =(DRM+1)/32, =4 bits, =[11110000])
db 0 ; AL1: alloc 1 (=[00000000])
dw 0 ; CKS: check size (not removable)
dw 0 ; OFF: track offset (no system)
; BIOS functions
cboot:
; set cold boot defaults only
di ; ? make it obvious
lxi sp,spbase ; use space at top of RAM for stack
xra a ; zero in the accum
sta iobyte ; clear the iobyte
sta usrdsk ; select user and disk zero
mvi c,0 ; select disk 0
call seldsk
call home ; Sets Disk and Track 0
; setup 82C52 SIO: 9600,8N1 on RST7.5
mvi a,05bh ; set SOD low, reset RST7.5 and unmask RST7.5
sim
mvi a,03Ch ; 8N1
sta 0041h
mvi a,066h ; Use interrupt with DTR/CTS
sta 0042h
mvi a,02Ah ; Set 9600 buad (using a 5MHz CPU clock)
sta 0043h
; display logon message
lxi h,signon ; Show cold boot message
call prmsg ; print message
jmp gocpm ; initialize and go to cp/m
wboot:
; reload CP/M but skip boot on sector 1
di ; ? make it obvious
lxi sp,spbase ; use space at top of RAM for stack
; setup system disk
mvi c,0 ; select disk 0
call seldsk
call home ; Sets Disk and Track 0
; load CP/M
lxi d,cbase ; start of boot dst
lxi h,0e080h ; start of boot src (start at sector 2)
mvi c,sectors ; sectors per track
mvi b,systrks ; track count (four system tracks)
push b ; save
dcr c ; skip sector 1
wboot$nextsect:
mvi b,128 ; sector size
wboot$copysect:
mov a,m
inx h
stax d
inx d
dcr b
jnz wboot$copysect
dcr c
jnz wboot$nextsect
pop b
dcr b
push b
jnz wboot$nextsect
jmp gocpm
; set parameters and go to cp/m
gocpm:
mvi a,0c3h ; c3h is a jmp instruction
sta 0000h ; for jmp to wboot
lxi h,wstart ; wboot entry point
shld 0001h ; set address field for jmp at 00000h
sta 0005h ; for jmp to bdos
lxi h,bdos ; bdos entry point
shld 0006h ; address field of Jump at 0005h to bdos
sta rst7.5 ; for jmp to getchar
lxi h,getchar ; get serial data input entry point
shld rst7.5+1 ; set address field of ISR to get serial char
lxi b,80h ; default dma address is 80h
call setdma
mvi a,4 ; define four drives
sta drives
dcr a ; test if usrdsk>=drives
mov c,a
lda usrdsk ; get current user and disk number
cmp c
jc gocpm$end
mvi a,00h
gocpm$end:
sta usrdsk
mov c,a ; send to the ccp
ei ; enable the interrupt system
jmp cbase ; go to cp/m
; get serial character and put in the ring buffer (called by RST7.5)
; assume a 10 MHz crystal: baud=9600,8N1
getchar:
di ; no interrupts
push psw
push b
push d
push h
lda 40h ; Read 82C52 register
; Save in ring buffer
getchar$5:
lda rput ; rbuf put ptr (0-f)
mov e,a
lxi h,rbuf
mvi d,00h
dad d
inr a
ani 0fh
sta rput
mov m,c
pop h
pop d
pop b
pop psw
ei
ret
signon: ; signon message
db cr,lf,lf
db 'my CP/M 2.2 V3'
db cr,lf,0
; print zero delimited string pointed to by
prmsg:
mov a,m
ora a
rz ; exit on zero
; more to print
push h
mov c,a
call putchar
pop h
inx h
jmp prmsg
; console status, return 0ffh if character ready, 00h if not
const:
lda rput
mov c,a
lda rget
sub c
rz
mvi a,0ffh
ret
; get console character into A (blocking)
conin:
lda rget
mov c,a
lda rput
sub c
jz conin ; wait for a character
lxi h,rbuf
mvi b,00h
dad b
mov a,c
inr a
ani 0fh
sta rget
mov a,m
ani 7fh
mov c,a
ret
; put character to serial out from register C
; assumes a 10 MHz crystal: baud=9600,8,N,1
putchar:
push psw
mov a,c
sta 0040h
pop psw
ret
conout:
di ; Acccept no serial in while serial out
call putchar ; ? putchar does not alter interrupts
ei
ret
; list character from register c
list:
ret ; null subroutine
; return list status (0 if not ready, 1 if ready)
listst:
xra a ; 0 is always ok to return
ret
; punch character from register C
punch:
ret ; null subroutine
; reader character into register a from reader device
reader:
mvi a,1ah ; enter end of file for now (replace later)
ani 7fh ; remember to strip parity bit
ret
; move to the track 0 position of current drive
home:
; translate this call into a settrk call with parameter 0
mvi c,0 ; select track 0
mvi b,0
call settrk
ret ; we will move to 00 on first read/write
; select disk given by register c
seldsk:
lxi h,0000h ; error return code
lda drives
cmp c
rc ; out of range
rz ; out of range
mov a,c
sta diskno
; select disk selected but page is reset!
rlc ; provision for four disks
rlc
ani 0c0h ; resets page to 0
out 0ffh ; output to disk/page register
; compute Disk Parameter Header address
lda diskno
mov l, a ; l=disk number 0, 1, 2, 3
mvi h, 0 ; high order zero
dad h
dad h
dad h
dad h
lxi d,dpbase
dad d ; hl=dpbase+diskno*16
ret
;
settrk: ; set track given by registers
mov h,b
mov l,c
shld track
ret
;
setsec: ; set sector given by register c
mov a, c
sta sector
ret
; translate the sector using the translate table [de]
sectran:
xchg ; set hl=translation table
dad b ; set hl=hl+sector
mov l,m ; get translated sector
mvi h,0 ; ? sector numbers between 1 and 255
ret ; return with translated sector in
setdma:
; set dma address given by registers
mov h,b ; high order address
mov l,c ; low order address
shld dmaad ; save the address
ret
; calculate disk number, disk page, track and sector address
; returns = DDTT TTTT 111T TSSS S000 0000
calcdskadr:
; set disk number (0-3)
lda diskno ; load diskno number
rrc
rrc
ani 0c0h
mov c,a ; DD00 0000
; set low byte of track number
lda track ; load low byte of track number
rrc
rrc
ani 03fh
ora c ; DDTT TTTT
mov c,a ; save
; set low nibble of sector number
lda sector ; load sector number
dcr a ; less one for memory address
stc
rar
mov d,a ; 1SSS SSSS
mvi a,00h
rar ; S000 0000
mov e,a ; save
mvi a,0e7h
ora d ; 1110 0SSS
; set low nibble of low byte of track number
lda track ; load low byte of track number
rlc
rlc
rlc
ani 18h
ora d ; 111T TSSS
mov d,a ; save
ret
; read sector from disk
read:
lhld dmaad ; set DMA address
call calcdskadr ; calculate disk address
mov a,c ; out (set) disk number and page
out 0ffh
mvi b,80h ; sector size
read$1:
ldax d
inx d
mov m,a
inx h
dcr b
jnz read$1
xra a ; always succeeds
ret
; write sector from disk
write:
call calcdskadr ; calculate disk address
lhld dmaad ; set DMA address
mov a,c ; out (set) disk number and page
out 0ffh
mvi b,80h ; sector size
xchg ; swap destination and source
di ; ? timing critial
write$page: ; write page (128b)
ldax d
inx d
mov m,a
inx h
dcr b
jnz write$page
push psw ; reset rst7.5
mvi a,010h
sim
pop psw
ei
; wait for flash
dcx h
write$wait:
cmp m
jnz write$wait
inx h
xra a ; always succeeds
ret
; BIOS data area
drives: ds 1 ; number of disk drives 1-16 max
diskno: ds 1 ; disk number 0-15 max
track: ds 2 ; track number 0-65535 max
sector: ds 1 ; sector number 1-255 max
dmaad: ds 2 ; direct memory address
; scratch ram area for bdos use
dirbf: ds 128 ; scratch directory area
all00: ds 31 ; allocation vector 0 (=DSM/8+1)
all01: ds 31 ; allocation vector 1 (=DSM/8+1)
all02: ds 32 ; allocation vector 2 (=DSM/8+1)
all03: ds 32 ; allocation vector 3 (=DSM/8+1)
chk00: ds 16 ; check vector 0 (CKS=0, therefore not used)
chk01: ds 16 ; check vector 1 (CKS=0, therefore not used)
chk02: ds 16 ; check vector 2 (CKS=0, therefore not used)
chk03: ds 16 ; check vector 3 (CKS=0, therefore not used)
; Serial use:
rbuf: ds 16 ; ring buffer for serial data
rget: db 0 ; ring buffer get pointer
rput: db 0 ; ring buffer put pointer
bitcnt: db 33 ; bit count for 9600 baud and 10MHz crystal
end
I willdouble check the code tomorrow before uploading the code to the system disk (e.i. W29C020).
Reblocking
Once I get the W29C020 working I need to code the reblocking for the W29C040 as it has a 256b page size (rather than 128b as per the W29C020).
MyCP/M EMU
I rebuilt my EMU for the new hardware. Updated the Intel HEX import of HEX16 files. Picked up a number of errors with CBIOS. On the EMU it now displays the bootup message.
Some problems with reading the console which seems to be an EMU error. The interrupt is working but there seems to be a memory conflict somewhere.
I am tempted to program the Flash chip and try my luck. No luck.
I have been working a few hours every few days on this and I have tracked down the problem to a jump into the "read" cbios routine. Still difficult to work out where the jump came from. Basically, you can trace the code but finding the error in millions of instructions is difficult. Still working on it.
TBC...
AlanX
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