Bugfix in outmdm (output buffer flush)

[kermit-80.git] / cpxpcw.asm

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:  <D.P.Arnot@edinburgh.ac.uk>
; 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 C.J.MILES@UK.AC.UMRCC
;       Hangup phone and clear screen options added to
;       terminal mode.
;
; edit 4 23 March 1987 by C.J.MILES@UK.AC.UMRCC
;       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 (C.J.MILES@UK.AC.UMRCC)
;       (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:
;
;  ian@latlog.uucp
;  ...seismo!mcvax!ukc!latlog!ian
; or c/o OBSchou@uk.ac.lut.multics
;
; ... 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