CP/M/CPM_CDROM.iso/enterprs/cpm/utils/a/bios2rsx.lzh/BIOS2RSX.ASM

Assembly Source File | 1991-01-16 | 11.5 KB | 540 lines

;
    title    'CP/M 2.2 BIOS RSX'
;
;    18Jan84        By Mike Griswold
;
;    This RSX will provide CP/M 2.2 compatible BIOS support
;    for CP/M 3.x.  Primarily it performs logical sector
;    blocking and deblocking needed for some programs.
;    All actual I/O is done by the CP/M 3.0 BIOS.
;
; Typed in from the Dr. Dobb's Journal article in the July 84
;  issue.                    mabry
;
; Modified 9 July 1984 to run on an 8085 rather than just a Z80 !
;  Also added trap for BDOS call 12 (version number) and returns
;  the indication that the calling program is running under
;  version 2.2 of CP/M.  This is necessary for programs that
;  are written to trap a CP/M Plus environment but not able to
;  handle the physical sector I/O of a CP/M Plus BIOS.
;                        mabry
;
    cseg
;
;    This equate is the only hardware dependent value.
;    It should be set to the largest sector size that
;    will be used.
;
max$sector$size:    equ    256

cr    equ    0dh
lf    equ    0ah
;
;
;    RSX prefix structure
;
    db    0,0,0,0,0,0
entry:    jmp    boot
next:    db    jmp        ; jump
    dw    0        ; next module in line
prev:    dw    0        ; previous module
remove:    db    0ffh        ; remove flag
nonbmk:    db    0
    db    'BIOS2.21'
    db    0,0,0
;
;    The CP/M 3.0 BIOS jump table is copied here
;    to allow easy access to 1st routines.  The disk
;    I/O routines are potentially in banked memory
;    so they cannot be called directly.
;
xwboot:    jmp    0        ; warm boot
xconst:    jmp    0
xconin:    jmp    0
xconout:jmp    0
xlist:    jmp    0
xauxout:jmp    0
xauxin:    jmp    0
    jmp    0
    jmp    0
    jmp    0
    jmp    0
    jmp    0
    jmp    0
    jmp    0
xlistst:jmp    0
;
;    Signon message
;
signon:    db    cr,lf,'BIOS ver 2.21 ACTIVE',cr,lf,0
;
;    Cold boot
;
boot:    push    psw        ; a BDOS call is in progress, save cpu state
    push    h        ;  so save cpu state
    push    d
    push    b
    lda    first        ; is this the first time through ?
    ora    a
    jz    boot10        ; jump if no
    xra    a        ; reset first time through flag
    sta    first
    call    init        ; initialize BIOS variables
    lhld    1        ; save the CP/M 3.0 BIOS jump
    shld    old$addr    ;  at location 0
    lxi    d,xwboot    ; set up to move jump table
    lxi    b,15*3        ; byte count

;    ldir
boot05:
    mov    a,m
    stax    d
    inx    h
    inx    d
    dcr    c        ; This is cheating, but 15*3 < 256
    jnz    boot05

    lxi    h,wbt        ; substitute new jump address
    shld    1
    lxi    h,signon    ; sound off
    call    prmsg
;
; We check to see if CP/M version number is requested via BDOS
;  function 12.  If so, return 2.2.
;
boot10:
    mov    a,c        ; BDOS function number
    cpi    12        ; version call ?
    jnz    boot15        ; if no, then continue
    pop    b
    pop    d
    pop    h
    pop    psw
    lxi    h,0022h        ; flag CP/M and version 2.2
    ret
boot15:
    pop    b        ; restore BDOS call state
    pop    d
    pop    h
    pop    psw
    jmp    next        ; carry on
;
;    Warm boot
;
wboot:    lhld    old$addr
    shld    1        ; restore normal BIOS address
    jmp    0        ; jump to CP/M 3.0 warm boot
;
;    Initialize BIOS internal variables for cold boot
;
init:    xra    a
    sta    hstwrt        ; host buffer written
    sta    hstact        ; host buffer inactive
    lxi    h,80h
    shld    dmaadr
    ret
;
;    Routine to call banked BIOS routines via BDOS
;    function 50.  All disk I.O calls are made through
;    here.
;
xbios:    sta    biospb        ; set BIOS function
    mvi    c,50        ; direct BIOS call function
    lxi    d,biospb    ; BIOS parameter block
    jmp    next        ; jump to BDOS
;
biospb:    db    0        ; BIOS function
areg:    db    0        ; A register
bcreg:    dw    0        ; BC register
dereg:    dw    0        ; DE register
hlreg:    dw    0        ; HL register
;
;    Home disk.
;
home:    lda    hstwrt        ; check if pending write
    ora    a
    cnz    writehst    ; dump buffer to disk
    xra    a
    sta    hstwrt        ; buffer written
    sta    hstact        ; buffer inactive
    sta    unacnt        ; zero alloc count
    sta    sektrk        ; zero track count
    sta    sektrk+1
    ret
;
;    Set track.
;
settrk:;sbcd    sektrk
    mov    l,c        ; track number to HL
    mov    h,b
    shld    sektrk
    ret
;
;    Align jump table on next page boundary.  This is needed
;    for programs that cheat when getting the addresses of
;    BIOS jump table entries.
;
    ds    16
;
;    BIOS Jump Table
;
cbt:    jmp    wboot        ; cold boot entry
wbt:    jmp    wboot        ; warm boot entry
    jmp    xconst        ; console status
    jmp    xconin        ; console input
    jmp    xconout        ; console output
    jmp    xlist        ; list output
    jmp    xauxout        ; aux device output
    jmp    xauxin        ; aux device input
    jmp    home        ; home disk head
    jmp    seldsk        ; select drive
    jmp    settrk        ; select track
    jmp    setsec        ; select sector
    jmp    setdma        ; set dma address
    jmp    read        ; read a sector
    jmp    write        ; write a sector
    jmp    xlistst        ; list status
    jmp    sectran        ; sector translation
;
;    Select disk.  Create a fake DPH for programs
;    that might use it.
;
seldsk:    mov    a,c        ; requested drive number
    sta    sekdsk
    sta    bcreg        ; set C reg in BIOSPB
    mvi    a,9        ; BIOS function number
    call    xbios        ; CP/M 3.0 select
    mov    a,h
    ora    l        ; check for HL=0
    rz            ; select error
    mov    e,m        ; get address of xlat table
    inx    h
    mov    d,m
    xchg
    shld    xlat        ; save xlat address
    lxi    h,11        ; offset to dpb address
    dad    d
    mov    e,m        ; fetch address of dpb
    inx    h
    mov    d,m
    xchg
    shld    dpb        ; address of dpb
    mov    a,m        ; cpm sectors per track
    sta    spt
    inx    h
    inx    h        ; point to block shift mask
    inx    h
    mov    a,m
    sta    bsm        ; save block shift mask
    lxi    d,12        ; offset to psh
    dad    d
    mov    a,m
    sta    psh        ; save physical shift factor
    lxi    h,dph        ; return DPH address
    ret
;
;    This fake DPH holds the adresses of the actual
;    DPB.  The CP/M 3.0 DPH is *not* understood
;    by CP/M 2.2 programs.
;
dph:    equ    $
    dw    0        ; no translation
    ds    6        ; scratch words
    ds    2        ; directory buffer
dpb:    ds    2        ; DPB
    ds    2        ; CSV
    ds    2        ; ALV
;
;    Set dma.
;
setdma:;sbcd    dmaadr
    mov    l,c        ; dma number to HL
    mov    h,b
    shld    dmaadr
    ret
;
;    Translate sectors.  Sectors are not translated yet.
;    Wait until we know the physical sector number.
;    This works fine as long as the program trusts
;    the BIOS to do the translation.  Some programs
;    access the XLAT table directly to do their own
;    translation.  These programs will get the wrong
;    idea about the disk skew but it should cause no
;    harm.
;
sectran:mov    l,c        ; return sector in HL
    mov    h,b
    ret
;
;    Set sector number.
;
setsec:    mov    a,c
    sta    seksec
    ret
;
;    Read the selected CP/M sector.
;
read:    mvi    a,1
    sta    readop        ; read operation
    inr    a        ; a=2 (wrual)
    sta    wrtype        ; treat as unalloc
    jmp    alloc        ; perform read
;
;    Write the selected CP/M sector.
;
write:    xra    a
    sta    readop        ; not a read operation
    mov    a,c
    sta    wrtype        ; save write type
    cpi    2        ; unalloc block?
    jnz    chkuna
;
;    Write to first sector of unallocated block.
;
    lda    bsm        ; get block shift mask
    inr    a        ; adjust value
    sta    unacnt        ; unalloc record count
    lda    sekdsk        ; set up values for
    sta    unadsk        ;  writing to an unallocated
    lda    sektrk        ;  block
    sta    unatrk
    lda    seksec
    sta    unasec
;
chkuna:    lda    unacnt        ; any unalloc sectors
    ora    a        ;  in this block?
    jz    alloc        ; skip if not
    dcr    a        ; unacnt = unacnt - 1
    sta    unacnt
    lda    sekdsk
    lxi    h,unadsk
    cmp    m        ; sekdsk = unadsk ?
    jnz    alloc        ; skip if not
    lda    sektrk
    lxi    h,unatrk
    cmp    m        ; sektrk = unatrk ?
    jnz    alloc        ; skip if not
    lda    seksec
    lxi    h,unasec
    cmp    m        ; seksec = unasec ?
    jnz    alloc        ; skip if not
    inr    m        ; move to next sector
    mov    a,m
    lxi    h,spt        ; addr of spt
    cmp    m        ; sector > spt ?
    jc    noovf        ; skip if no overflow
    lhld    unatrk
    inx    h
    shld    unatrk        ; bump rack
    xra    a
    sta    unasec        ; reset sector count
noovf:    xra    a
    sta    rsflag        ; don't pre-read
    jmp    rwoper        ; perform write
;
alloc:    xra    a        ; requires pre-read
    sta    unacnt
    inr    a
    sta    rsflag        ; force pre-read
;
rwoper:    xra    a
    sta    erflag        ; no errors yet
    lda    psh        ; get physical shift factor
    ora    a        ; set flags
    mov    b,a
    lda    seksec        ; logical sector
    lxi    h,hstbuf    ; addr of buffer
    lxi    d,128
    jz    noblk        ; no blocking
    xchg            ; shuffle registers
shift:    xchg
    rrc
    jnc    sh1
    dad    d        ; bump buffer address
sh1:    xchg
    dad    h        ; double offset
    ani    07fh        ; zero high bit

;    djnz    shift
    dcr    b
    jnz    shift

    xchg            ; HL=buffer addr
noblk:    sta    sekhst
    shld    sekbuf
    lxi    h,hstact    ; buffer active flag
    mov    a,m
    mvi    m,1        ; set buffer active
    ora    a        ; was it already?
    jz    filhst        ; fill buffer if not
    lda    sekdsk
    lxi    h,hstdsk    ; same disk ?
    cmp    m
    jnz    nomatch
    lda    sektrk
    lxi    h,hsttrk    ; same track ?
    cmp    m
    jnz    nomatch
    lda    sekhst        ; same buffer ?
    lxi    h,hstsec
    cmp    m
    jz    match
;
nomatch:
    lda    hstwrt        ; buffer changed?
    ora    a
    cnz    writehst    ; clear buffer

filhst:    lda    sekdsk
    sta    hstdsk
    lhld    sektrk
    shld    hsttrk
    lda    sekhst
    sta    hstsec
    lda    rsflag        ; need to read  ?
    ora    a
    cnz    readhst        ; yes
    xra    a
    sta    hstwrt        ; no pending write
;
match:    lhld    dmaadr
    xchg
    lhld    sekbuf
    lda    readop        ; which way to move ?
    ora    a
    jnz    rwmove        ; skip if read
    mvi    a,1
    sta    hstwrt        ; mark buffer changed
    xchg            ; hl=dma  de=buffer
;
rwmove:    lxi    b,128        ; byte count

;    ldir            ; block move
rwmv05:
    mov    a,m
    stax    d
    inx    h
    inx    d
    dcr    c        ; This is cheating, but 128 < 256
    jnz    rwmv05

    lda    wrtype        ; write type
    cpi    1        ; to directory ?
    jnz    exit        ; done
    lda    erflag        ; check for errors
    ora    a
    jnz    exit        ; don't write dir if so
    xra    a
    sta    hstwrt        ; show buffer written
    call    writehst    ; write buffer
exit:    lda    erflag
    ret
;
;    Disk read.  Call CP/M 3.0 BIOS to fill the buffer
;    with one physical sector.
;
readhst:
    call    rw$init        ; init CP/M 3.0 BIOS
    mvi    a,13        ; read function number
    call    xbios        ; read sector
    sta    erflag
    ret
;
;    Disk write.  Call CP/M 3.0 BIOS to write one
;    physical sector from buffer.
;
writehst:
    call    rw$init        ; init CP/M 3.0 BIOS
    mvi    a,14        ; write function number
    call    xbios        ; write sector
    sta    erflag
    ret
;
;    Translate sector.  Set CP/M 3.0 track, sector,
;    DMA buffer and DMA bank.
;
rw$init:
    lda    hstsec        ; physical sector number
    mov    l,a
    mvi    h,0
    shld    bcreg        ; sector number in BC
    lhld    xlat        ; address of xlat table
    shld    dereg        ; xlat address in DE
    mvi    a,16        ; sectrn function number
    call    xbios        ; get skewed sector number
    mov    a,l
    sta    actsec        ; actual sector
    shld    bcreg        ; sector number in BC
    mvi    a,11        ; setsec function number
    call    xbios        ; set CP/M 3.0 sector
    lhld    hsttrk        ; physical track number
    shld    bcreg        ; track number in BC
    mvi    a,10        ; settrk function number
    call    xbios
    lxi    h,hstbuf    ; sector buffer
    shld    bcreg        ; buffer address in BC
    mvi    a,12        ; setdma function number
    call    xbios
    mvi    a,1        ; DMA bank number
    sta    areg        ; bank number in A
    mvi    a,28        ; setbnk function number
    call    xbios        ; set DMA bank
    ret
;
;    Print message at HL until null.
;
prmsg:    mov    a,m
    ora    a
    rz
    mov    c,m
    push    h
    call    xconout
    pop    h
    inx    h
    jmp    prmsg
;
;    disk i/o buffer
;
hstbuf:    ds    max$sector$size
;
;    variable storage area
;
sekdsk:    ds    1        ; logical disk number
sektrk:    ds    2        ; logical track number
seksec:    ds    1        ; logical sector number
;
hstdsk:    ds    1        ; physical disk number
hsttrk:    ds    2        ; physical track number
hstsec:    ds    1        ; physical sector number
;
actsec:    ds    1        ; skewed physical sector
sekhst:    ds    1        ; temp physical sector
hstact:    ds    1        ; buffer ative flag
hstwrt:    ds    1        ; buffer changed flag
;
unacnt:    ds    1        ; unallocated sector cunt
unadsk:    ds    1        ; unalloc disk number
unatrk:    ds    2        ; unalloc track number
unasec:    ds    1        ; unalloc sector number
sekbuf:    ds    2        ; logical sector address in buffer
;
spt:    ds    1        ; cpm sectors per track
xlat:    ds    2        ; xlat address
bsm:    ds    1        ; block shift mask
psh:    ds    1        ; physical shift factor
;
erflag:    ds    1        ; error reporting
rsflag:    ds    1        ; force sector read
readop:    ds    1        ; 1 if read operation
rwflag:    ds    1        ; physical read flag
wrtype:    ds    1        ; write operation type
dmaadr:    ds    2        ; last dma address
oldaddr:ds    2        ; address of old BIOS
;
first:    db    0ffh        ; first time through flag, set on load

    end