Columbia Kermit/kermit.zip/cpm80/cpxpcw.asm

Assembly Source File | 2020-01-01 | 23KB | 913 lines

IF NOT lasm
.printx * CPXPCW.ASM *
ENDIF    ;NOT lasm
;
; KERMIT - (Celtic for "FREE")
;
; This is the CP/M-80 implementation of the Columbia University
; KERMIT file transfer protocol.
;
; Version 4.08
;
; Copyright June 1981,1982,1983,1984,1985
; Columbia University
;
; Originally written by Bill Catchings of the Columbia University Center for
; Computing Activities, 612 W. 115th St., New York, NY 10025.
;
; This file contains the system-dependent code and data for KERMIT
; on the Amstrad range of personal computers.
;
;
; Revision history:
;
;edit 9, 22-Jan-1991 by MF. Added "sysinit" code at "init04" from Kermit
;    version 4.08 which had been left out of version 4.09 to reserve
;    space for the Amstrad's I/O buffers. Amstrad Kermit now stores
;    files correctly (version 4.09 had garbled files). Again,
;    this fix comes from Mr. D. P. Arnot of the Scottish Agricultural
;    College in the UK.
;edit 8, 16-Jan-1991 by MF. Added a "bs" left out of "delstr" per
;    instruction from David P. Arnot of Scottish Agricultural
;    College, Auchincruive, Ayr, UK.
;    E-mail:  <[e-mail]>
; edit 7, 22 July 1987 by OBSchou to massage code to fit with CPXCOM.ASM
;    Had to rename bcnout to bcnot as the former label clashed with
;    one of the same name in CPXCOM.ASM.  Sorry, folks.
;
; edit 6, 14th July, 1987 by OBSchou for Phillip Wade, Hull University
;    Computer Centre.  Change to delchr routine for PCW machines,
;    as character 127 decimal is a printing character on
;    the Amstrad PCW.  The routine has been replaced
;    by a bs,space,bs,bs string. (OBS Comment - why a total of THREE bs?)
;
; edit 5 9 May 1987 by [e-mail]
;    Hangup phone and clear screen options added to
;    terminal mode.
;
; edit 4 23 March 1987 by [e-mail]
;    Use direct input drom SIO for CPC machines instead
;    of using BDOS. Improvement reduces time for file
;    transfer to 65% of time used by BDOS method.
;    Add reverse Prestel baud rate.
;
; edit 3 20 March 1987 by Chris Miles ([e-mail])
;    (Greater Manchester Archaeological Unit, Manchester Univ.).
;    Added support for Amstrad CPC CP/M Plus machines,
;    Added 31250 baud rate option,
;    Bug fixed in sending BREAK,
;    Bug fixed in 1200/75 baud setup
;    Machine and CP/M version checks added.
;
; edit 2 11 Febuary, 1987 by OBSchou for Ian Young.
;    Changes to the send break routine to change two lines of code from
;        ori    018h        ; send break, Tx enable
;    and    ori    0008h        ; Tx enable
;
;    to    ori    01ah        ; send break, Tx enable, RTS
;    and    ori    00ah        ; Tx enable, RTS
;
;    This is a bug fix to hopefully keep RTS actve during breaks.
;
; [Ed. (OBSchou) 21/1/87.
; This file linked FROM cpxsys.asm, so do NOT rename this
; file.  The diffculty of needing a HUGE CPXSYS.ASM file on your floppy
; only to act as a switcher remains, but hopefully will be better in
; the future.  If you ARE stuck, then rename this CPXSYS.ASM but add the
; label SYSEDT: to the FAMILY label.  A bit messy.]
;
;
; The "author" of this system-dependent file is:
;
;  Ian A. Young
;  Lattice Logic Ltd
;  9 Wemyss Place
;  Edinburgh
;
; Some other addresses:
;
;  [e-mail]
;  ...seismo!mcvax!ukc!latlog!ian
; or c/o [e-mail]
;
; ... although much of the code concerned was written by others.
;


; Keep module name, edit number, and last revision date in memory.

;sysedt:    db    'CPXSYS.ASM (36) 20-Mar-87$'
family:    db    'CPXPCW.ASM (9)  22-Jan-1991$'


;
; Assembly-time message announcing which version we are building
;

IF pcw
.printx    * Assembling Amstrad PCW Kermit-80 *
ENDIF

IF cpc
.printx    * Assembling Amstrad CPC Kermit-80 *
ENDIF

;
; Miscellany of parameter settings
;
z80    EQU    TRUE         ; all Amstrads have a Z80.
defesc    EQU    '\'-100O    ; The default escape character.
vtval    EQU    0         ; we don't need VT52 emulation

;
; Amstrad CPC machines use 16 bit I/O address decoding and therefore
; the Z80 instructions OUT (C),A and IN A,(C) must be defined.
;
outc    EQU    79edh        ; IN    A,(C)
inpc    EQU    78edh        ; OUT    (C),A

;
; hardware information
;
; There is a Z80-DART (Mostek/SGS 8470) at I/O addresses E0..E3 (PCW)
; and FADC..FADD (CPC), and a 8253 programmable divider running it at
; E4..E7 (PCW) and FBDC..FBDF (CPC)
;

input    EQU    01h        ; input data available
output    EQU    04h        ; output buffer ready

IF pcw
mnport    EQU    0E0h        ; data register for SIO
mnprts    EQU    0E1h        ; control register for SIO
ctc0    EQU    0E4h        ; 8253 load counter 0
ctc1    EQU    0E5h        ; 8253 load counter 1
ctcmod    EQU    0E7h        ; 8253 write mode word
ENDIF

IF cpc
mnport    EQU    0FADCh        ; data register for SIO
mnprts    EQU    0FADDh        ; control register for SIO
ctc0    EQU    0FBDCh        ; 8253 load counter 0
ctc1    EQU    0FBDDh        ; 8253 load counter 1
ctcmod    EQU    0FBDFh        ; 8253 write mode word
ENDIF

;
; SIO input buffering
;
siosz    EQU    4096        ; size of SIO input buffer
siomsk    EQU    4095        ; mask for wrapping buffer round

;
; Extended BIOS jump-block addresses; reached through USERF
;
sainit    EQU    00B6h        ; initialise SIO
sabaud    EQU    00B9h        ; set baud rate
saparm    EQU    00BCh        ; fetch SIO parameters
teask    EQU    00BFh        ; find out cursor position
cdvers    EQU    00E3h        ; get version numbers
cdinfo    EQU    00E6h        ; get BIOS system information

;
; System-dependent initialization
; Called once at program start.
sysxin:        ; continuation of system initialzation
;
; check for correct CP/M version
;
    mvi    c,12        ; get CP/M version BDOS call
    call    bdos
    mov    a,l        ; check if CP/M Plus
    cpi    31h
    jz    init08
    lxi    d,wrong2    ; point to error message
    call    prtstr
    mvi    c,0        ; warm boot
    call    bdos
;
init08:        ;[OBS] Moved the Cinfigured for message out as
        ;[OBS]   it is in CPXCOM.ASM
;
; get addresses of BIOS routines
;
; BIOS USERF is used to get to extended BIOS routines
;
    lhld    1        ; warm boot vector
    lxi    d,87        ; offset to USERF vector
    dad    d        ; DE now has USERF vector address
    shld    userf+1        ; ready for jumping to...
;
; BIOS routines for fast character I/O
;
    lhld    1        ; warm boot vector (#1)
    lxi    d,3
    dad    d        ; next is #2, CONST
    shld    bcnst+1
    dad    d        ; next is #3, CONIN
    shld    bcnin+1
    dad    d        ; next is #4, CONOUT
    shld    bcnot+1        ;[obs] Was bcnout, but this conflicts
                ;[obs] with a label in CPXCOM.ASM
    dad    d        ; next is #5, LIST
    shld    blist+1
    dad    d        ; next is #6, AUXOUT
    dad    d        ; next is #7, AUXIN
    shld    baxin+1
    lhld    1        ; warm boot vector again
    lxi    d,002Ah        ; offset to LISTST (#15)
    dad    d
    shld    lptstat+1
    lhld    1        ; warm boot vector again
    lxi    d,0033h        ; offset to AUXIST (#18)
    dad    d
    shld    baxist+1
;
; check if running on correct Amstrad
;
    call    userf
    dw    cdvers
IF pcw
    cpi    0
ENDIF
IF cpc
    cpi    1
ENDIF
    jnz    init06
    lxi    d,wrong1    ; point to error message
    call    prtstr
    mvi    c,0
    call    bdos
;
; verify presence of SIO board by asking the BIOS.
;
init06:    call    userf        ; C gets 00 if not fitted
    dw    cdinfo
    xra    a        ; a <- 0
    ora    c        ; zero => no serial port
    jnz    init03        ; non-zero => OK
    lxi    d,nosio        ; snooty message...
    call    prtstr
    mvi    c,0        ; warm boot out of here
    call    bdos
init03:
;
; find initial baud rate and other information
;
    call    userf        ; gives B=rx baud, C=tx baud, D=stop bits,
                ; E=parity, H=rx bits, L=tx bits.
    dw    saparm        ; get SIO parameters
    push    h        ; save bit settings
    mov    a,b        ; if TX and RX speeds same, they are OK
    cmp    c
    jz    init01
    cpi    8        ; rx=1200?
    jnz    init02        ; no, can't be Prestel
    mov    a,c
    cpi    2        ; tx=75?
    jnz    init02        ; no, can't be Prestel
    lxi    b,0        ; otherwise 1200/75 comes out as 0s.
init01:    push    b        ; assign value to SPEED
    pop    h
    shld    speed
init02:                ; here if we leave it as is
    pop    h        ; get bit settings
    mov    a,l        ; no of TX data bits set
    sui    5        ; make into 00, 01, 10, 11.
    rrc
    rrc
    rrc
    sta    txbits        ; we may need it later
;
; set handshake mode: there are two parts to this, interrupts and
; hardware handshake. The MODE byte used by the firmware expresses
; this combination as -(int*2 + hand*1).  Thus, both options on would
; be (-3) or 0FDh.
;
; Here, we set the interrupt part of the mode on; it helps the BIOS cope.
; Unfortunately, >sigh<, according to Soft971, this will only work
; if you have BIOS V1.4 or higher.  I have no idea what would happen
; if we tried random hanshake mode flags with lower versions, so we
; just skip over if it would be dangerous...
;
    call    userf        ; fetch all parameters
    dw    saparm
    sta    orgmode        ; remember original mode for later

    call    userf        ; get BIOS version to B,C
    dw    cdvers
    mov    a,b        ; BIOS major version number (eg 1)
    ora    a        ; if zero, too low...
    jz    init04
    cpi    1        ; if not 1, definitely OK
    jnz    init05
    mov    a,c        ; otherwise, its 1.X; want >= 4
    cpi    4
    jm    init04        ; <4 => too low

init05:    call    userf        ; get the original flags back
    dw    saparm
    xri    0FFh        ; make mode into bit mask
    inr    a
    ori    2        ; set interrupt mode
    xri    0FFh        ; turn back into mode value
    inr    a
    call    userf        ; feed change back to BIOS
    dw    sainit
init04:                ; come here if not setting mode

; Locate large buffers for multi-sector I/O and SIO input buffering.
; Space above ovlend is available for buffers; we have pretty well the machine
; to ourselves in an Amstrad PCW because they all gave 61K TPAs. We don't even
; bother to perform any checking.
; We don't want to use more than maxsec for disk buffers because
; if we use too many, the remote end could time out while we're
; writing to disk.  maxsec is system-dependent, but for now we'll just
; use 8Kbytes.  If you get retransmissions and other protocol errors after
; transferring the first maxsec sectors, lower maxsec.
;
maxsec  EQU     (8*1024)/bufsiz ; 8K / number of bytes per sector

        lxi     h,ovlend+siosz  ; get start of buffer
        shld    bufadr          ; store in linkage section
        mvi     a,maxsec        ; get size of buffer, in sectors
        sta     bufsec          ; store that, too.


        ret                     ; return from system-dependent routine

;
; message complaining about wrong Amstrad machine
;
wrong1:    db    'Error -   This Kermit will only run on the Amstrad '
IF pcw
    db    'PCW 8256/8512'
ENDIF
IF cpc
    db    'CPC 464/664/6128'
ENDIF
    db    cr,lf,'$'
;
; message complaining about version of CP/M being used
;
wrong2:    db    'Error - Incorrect CP/M version, needs CP/M 3.x'
    db    cr,lf,'$'
;
; message complaining of no SIO board
;
nosio:    db    'Error -   No SIO option fitted to this machine'
    db    cr,    lf, '$'

;
; jumps to BIOS character I/O routines.
; Addresses filled in by initialisation code above.
;
bcnst:    jmp    $-$        ; console status
bcnin:    jmp    $-$        ; console input
bcnot:    jmp    $-$        ; console output [obs - was bcnout]
blist:    jmp    $-$        ; printer output
baxin:    jmp    $-$        ; aux port input
baxist:    jmp    $-$        ; aux port status
lptstat:jmp    $-$        ; printer status

;
; Other BIOS routines
;
userf:    jmp    $-$        ; call extended BIOS function

;
; saved value of some original parameters
;
orgmode:ds    1
txbits:    ds    1

;
; system-dependent termination processing
; If we've changed anything, this is our last chance to put it back.
sysexit:
    call    userf        ; fetch firmware parameters
    dw    saparm
    lda    orgmode        ; replace with original mode
    call    userf        ; inform BIOS
    dw    sainit
    ret

;
; system-dependent processing for start of CONNECT command
;
syscon:
    lxi    d,conmsg    ; how to get escape char message
    call    prtstr
    ret

conmsg:        ; Messages printed when entering transparent (CONNECT) mode:
IF pcw
    db    '(Use boxed minus key next to space bar to generate a Control-\)'
ENDIF
    db    cr,lf,'$'

;
; syscls - system-dependent close routine
; called when exiting transparent session.
;
syscls:
    ret

;
; sysinh - help for system-dependent special functions.
; called in response to <escape>?, after listing all the
; system-independent escape sequences.
;
sysinh:
    lxi    d,inhlps    ; we got options...
    call    prtstr        ; print them.
    ret

;
; additional, system-dependent help for transparent mode
; (two-character escape sequences)
;
inhlps:
    db    cr,lf,'B  Transmit a BREAK'
    db    cr,lf,'H  Hangup using DTR'
    db    cr,lf,'W  Wipe screen clear'
    db    '$'            ;[hh] table terminator

;
; sysint - system dependent special functions
; called when transparent escape character has been typed;
; the second character of the sequence is in A (and in B).
; returns:
;         non-skip: sequence has been processed
;         skip    : sequence was not recognized
;
sysint:    ani    137O        ; convert lower case to upper, for testing...
    cpi    'B'        ; send break ?
    jz    sendbr        ; yes, go do it.  return nonskip when through.
    cpi    'H'        ; hang up ?
    jz    hangup
    cpi    'W'        ; clear screen ?
    jz    clrtop
    jmp    rskp        ; take skip return - command not recognized.

;
; Hangup (drop DTR) and Break send routine
;

hangup:
    mvi    d,0ah        ; set up hangup bit mask
    mvi    e,255        ; time for hangup is 2 1/2 secs
    jmp    setbit        ; skip Tx empty test

sendbr:
    mvi    d,9ah        ; set up break bit mask
    mvi    e,30        ; time for break is 300 ms

sndbr1:    mvi    a,1        ; select Read Register 1

IF pcw    ; allow 8 bit I/O instructions
    out    mnprts
    in    mnprts        ; read the contents
ENDIF

IF cpc    ; use 16 bit I/O instructions
    lxi    b,mnprts
    dw    outc        ; OUT    (C),A
    dw    inpc        ; IN    A,(C)
ENDIF

    ani    1        ; test "all done" flag
    jz    sndbr1        ; loop until it's nonzero.
;
; Next, set the break or hangup bit on the SIO.
;
setbit:
    mvi    a,5        ; select Write Register 5
IF pcw
    out    mnprts
ENDIF
IF cpc
    dw    outc        ; OUT    (C),A
ENDIF
    lda    txbits        ; get txbits (already in correct bit positions)
    ora    d        ; send break, Tx Enable, RTS
IF pcw
    out    mnprts
ENDIF
IF cpc
    dw    outc        ; OUT    (C),A
ENDIF

;
; Now, delay for duration of hangup or break
;
    mov    a,e        ; delay count
    call    delay
;
; Time's up. Put transmitter back in normal state and return.
;
    mvi    a,5        ; select Write Register 5
IF pcw
    out    mnprts
ENDIF
IF cpc
    lxi    b,mnprts
    dw    outc        ; OUT    (C),A
ENDIF
    lda    txbits        ; get txbits again
    ori    8ah        ; Reset break, Tx Enable, RTS
IF pcw
    out    mnprts
ENDIF
IF cpc
    dw    outc        ; OUT    (C),A
ENDIF
    ret            ; done.

;
; sysflt - system-dependent filter
; called with character in E.
; if this character should not be printed, return with A = zero.
; preserves bc, de, hl.
; note: <xon>,<xoff>,<del>, and <nul> are always discarded.
;
sysflt:
    mov    a,e        ; get character for testing
    ret
;
; system-dependent processing for BYE command.
;
sysbye:
    ret

;
; This is the system-dependent command to change the baud rate.
; DE contains the two-byte value from the baud rate table; this
; value is also stored in 'speed'.
;
sysspd:
    push    d        ; move to HL for firmware
    pop    h
    mov    a,h        ; if h=0 then Prestel rates
    ora    a
    jnz    spd01        ; if not 1200/75 then skip
    lxi    h,0802H        ; else set 1200/75 into HL
    jmp    spd03        ; jump to normal setup

spd01:    cpi    11h        ; if h=11h then reverse Prestel
    jnz    spd02        ; if not 75/1200 then skip
    lxi    h,0208h        ; else set 75/1200 into HL
    jmp    spd03        ; jump to normal setup

spd02:    cpi    10h        ; if h=10h then 31250 baud
    jnz    spd03        ; if not 31250 then skip to normal setup
    mvi    a,36h        ; set 8253 for mode 2 binary count
    lxi    b,ctcmod    ; output to CTC mode register
    dw    outc
    lxi    b,ctc0        ; select transmit clock
    mov    a,4        ; timer value for 31250 (04h)
    dw    outc
    mov    a,0        ; timer value for 31250 (04h)
    dw    outc
    lxi    b,ctc0        ; select receive clock
    mov    a,4        ; timer value for 31250 (04h)
    dw    outc
    mov    a,0        ; timer value for 31250 (04h)
    dw    outc
    ret

spd03:    call    userf        ; set whatever we have now...
    dw    sabaud        ; using BIOS routine
    ret

;
; Speed tables
; (Note that speed tables MUST be in alphabetical order for later
; lookup procedures, and must begin with a value showing the total
; number of entries.  The speed help tables are just for us poor
; humans.
;
; db string length,string,divisor (2 identical bytes or 1 word)
;
spdtbl:    db    12h            ;18 entries
    db    03h,'110$', 03h,03h
    db    04h,'1200$', 08h,08h
    db    07h,'1200/75$', 00h,00h    ; real values faked up when required
    db    05h,'134.5$', 04h,04h
    db    03h,'150$', 05h,05h
    db    04h,'1800$', 09h,09h
    db    05h,'19200$', 0fh,0fh
    db    04h,'2400$', 0ah,0ah
    db    03h,'300$', 06h,06h
    db    05h,'31250$',10h,10h    ; flag to direct setup routine
    db    04h,'3600$', 0bh,0bh
    db    04h,'4800$', 0ch,0ch
    db    02h,'50$', 01h,01h
    db    03h,'600$', 07h,07h
    db    04h,'7200$', 0dh,0dh
    db    02h,'75$', 02h,02h
    db    07h,'75/1200$',11h,11h    ; real values faked up when required
    db    04h,'9600$', 0eh,0eh

sphtbl:    db    cr,lf,lf
    db    'Normal rates: 50    75    110   134.5 150   300   600'
    db    cr,lf
    db    '              1200  1800  2400  3600  4800  7200  9600  19200'
    db    cr,lf,lf
    db    'High speed  : 31250 (only between Amstrads)'
    db    cr,lf,lf
    db    'Split rates : 1200/75 (Rx=1200, Tx=  75)'
    db    cr,lf
    db    '              75/1200 (Rx=  75, Tx=1200)'
    db    cr,lf,'$'

;
; This is the system-dependent SET PORT command.
; HL contains the argument from the command table.
;
sysprt:
    ret

prttbl    equ    0        ; SET PORT is not supported
prhtbl    equ    0

;
; selmdm - select modem port
; selcon - select console port
; selmdm is called before using inpmdm or outmdm;
; selcon is called before using inpcon or outcon.
; preserves bc, de, hl.
;
selmdm:
selcon:
    ret

;
; Get character from console, or return zero.
; result is returned in A.  destroys bc, de, hl.
;
inpcon:
    call    bcnst        ; get console status
    ora    a        ; anything there?
    rz            ; no, forget it
    jmp    bcnin        ; yes, get the character

;
; Output character in E to the console.
; destroys bc, de, hl
;
outcon:
    mov    a,e        ; TAB?
    cpi    tab
    jz    out001
    mov    c,e        ; set correct arg register
    jmp    bcnot        ; output to console via BIOS [obs was bcnout]

;
; perform tab expansion ourselves
;
out001:    call    userf        ; get column in L
    dw    teask
    mov    a,l        ; a <- column 0..n
    ani    7        ; column 0..7
    xri    0FFh        ; not(col 0..7)
    adi    9        ; a is 8-(colf7)
out002:    ora    a        ; any left?
    rz            ; return if not
    dcr    a        ; one less now, anyhow
    push    psw        ; save over BIOS call (just in case)
    mvi    c,' '        ; print one space
    call    bcnot        ;[obs was bcnout]
    call    suck        ; in case any stuff coming in
    pop    psw        ; fetch count back
    jmp    out002        ; and go round again

;
; outmdm - output a char from E to the modem.
;  the parity bit has been set as necessary.
; returns nonskip; bc, de, hl preserved.
outmdm:
IF cpc
    push    b        ; save BC for CPC 16 bit I/O
ENDIF
outmd1:
    call    xsuck        ; keep checking for incoming characters
IF pcw
    in    mnprts        ; get the output done flag.
ENDIF
IF cpc
    lxi    b,mnprts
    dw    inpc        ; IN    A,(C)
ENDIF
    ani    output        ; is it set?
    jz    outmd1        ; if not, loop until it is.
    mov    a,e
IF pcw
    out    mnport        ; output it.
ENDIF
IF cpc
    lxi    b,mnport
    dw    outc        ; OUT    (C),A
    pop    b        ; restore BC
ENDIF
    ret

;
; get character from modem; return zero if none available.
; destroys bc, de, hl.
;
inpmdm:
    call    suck        ; get any characters pending
    lhld    sioct        ; count of chars in buffer
    mov    a,h        ; or together to get result
    ora    l
    rz            ; not got any, return now

    dcx    h        ; down count
    shld    sioct

    lhld    siord        ; read pointer
    mov    c,m        ; fetch character ** NB TO C FOR NOW **

    lxi    d,1-ovlend    ; bump pointer, subtract base
    dad    d
    mov    a,h        ; mask high byte of offset
    ani    siomsk/256
    mov    h,a
    lxi    d,ovlend    ; add in base again
    dad    d
    shld    siord

    mov    a,c        ; get to proper register
    ret

;
; flsmdm - flush comm line.
; Modem is selected.
; Currently, just gets characters until none are available.

flsmdm:    call    inpmdm        ; Try to get a character
    ora    a        ; Got one?
    jnz    flsmdm        ; If so, try for another
    ret            ; Receiver is drained.  Return.

;
; SIO input buffer handling.  The buffer pointers are held as pointers into
; the buffer. The read pointer
; is to the next unused character, the write pointer to the next unused space.
;
siord:    dw    ovlend        ; next char to read
siowr:    dw    ovlend        ; next char to write
sioct:    dw    0        ; number in buffer

xsuck:    push    d        ; save regs version of suck
    push    b
    push    h
    call    suck
    pop    h
    pop    b
    pop    d
    ret

;
; suck
;
; this routine is called whenever it would be possible that some
; characters might be available in the SIO device; they are all
; transferred (there may be up to 4 pending) to the buffer.
;
; all registers are destroyed
;
suck:
IF pcw
    call    baxist        ; check input status via BDOS
    ora    a        ; check if zero
ENDIF
IF cpc
    lxi    b,mnprts    ; get input status directly
    dw    inpc        ; IN A,(C)
    ani    input        ; mask for Rx ready
ENDIF
    rz            ; return if no

IF pcw
    call    baxin        ; fetch character via BDOS
ENDIF
IF cpc
    lxi    b,mnport    ; fetch character directly from SIO
    dw    inpc        ; IN A,(C)
ENDIF

    lhld    siowr        ; write pointer
    mov    m,a        ; put character

    lxi    d,1-ovlend    ; take off base, bump pointer
    dad    d
    mov    a,h        ; top byte of offset
    ani    siomsk/256    ; masked off
    mov    h,a
    lxi    d,ovlend    ; add on base again
    dad    d
    shld    siowr        ; replace pointer

    lhld    sioct        ; bump count in buffer
    inx    h
    shld    sioct

    jmp    suck        ; go round in case any more

;
; outlpt - output character in E to printer
; console is selected.
; preserves de.
outlpt:
    push    d        ; save DE in either case
    mov    c,e        ; correct arg register
    call    blist
    pop    d        ; restore saved register pair
    ret

;
; Screen manipulation routines
; csrpos - move to row B, column C
;
; csrpos for terminals that use a leadin sequence followed
;  by (row + 31.) and (column + 31.)
;  or (row) and (column)
;
csrpos:    push    b        ; save coordinates
    lxi    d,curldn    ; get cursor leadin sequence
    call    prtstr        ; print it
    pop    h        ; restore coordinates
    mov    a,h        ; get row
    adi    (' '-1)        ; space is row one
    mov    e,a
    push    h
    call    outcon        ; output row
    pop    h
    mov    a,l        ; get column
    adi    (' '-1)        ; space is column one
    mov    e,a
    jmp    outcon        ; output it and return

;
; delchr - make delete look like a backspace.  Unless delete is a printing
; character, we just need to print a backspace. (we'll output clrspc
; afterwards)
; For Kaypro and Vector General, delete puts a blotch on the screen.
; For Apple and Osborne 1, delete moves but doesn't print.
delchr:
IF pcw    ;[6] OBS for Phillip Wade
    lxi    d,delstr    ;[5] send a string rather than a single character
    call    prtstr

delstr:    db    bs,' ',bs,'$'    ;[OBS] Was bs,space,bs,bs
ENDIF    ;pcw

    mvi    e,bs        ;get a backspace
    jmp    outcon

; erase the character at the current cursor position
clrspc:    mvi    e,' '
    call    outcon
    mvi    e,bs        ;get a backspace
    jmp    outcon

; erase the current line
clrlin:    lxi    d,eralin
    jmp    prtstr

; erase the whole screen, and go home. preserves b (but not c)
clrtop:    lxi    d,erascr
    jmp    prtstr


IF pcw
sysver:    db    'Amstrad PCW with SIO option$'
ENDIF
IF cpc
sysver:    db    'Amstrad CPC with CP/M Plus$'
ENDIF

outlin:    db    esc,'H',esc,'J',cr,lf,'                $'

erascr:    db    esc,'H',esc,'J$'    ;Clear screen and go home.
eralin:    db    cr,esc,'K$'        ;Clear line.
curldn:    db    esc,'Y$'        ;cursor leadin
ttab:                    ;Table start location.
ta:    db    esc,'A$',0        ;Cursor up.
tb:    db    esc,'B$',0        ;Cursor down.
tc:    db    esc,'C$',0        ;Cursor right.
td:    db    esc,'D$',0        ;Cursor left
te:    db    esc,'E$',0        ;Clear display
tf:    db    '$',0,0,0        ;Enter Graphics Mode
tg:    db    '$',0,0,0        ;Exit Graphics mode
th:    db    esc,'H$',0        ;Cursor home.
ti:    db    esc,'I$',0        ;Reverse linefeed.
tj:    db    esc,'J$',0        ;Clear to end of screen.
tk:    db    esc,'K$',0        ;Clear to end of line.

ovlend    equ    $    ; End of overlay

    END