cbmsrc/DOS_1551/it2.src at master · mist64/cbmsrc · GitHub

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;  08/22/84  ds
;
        *  =  $c000
;
	.byte    $be    ;  chksum
author  .byte  'DAVID G SIRACUSA CBM COPYRIGHT 84'
;*****************************************************
;   p o r t    c o n f i g u r a t i o n    c m d s
;-----------------------------------------------------
;    process           cmd     data
;-----------------------------------------------------
;    listen            $81     $20
;    unlisten          $81     $3f
;    talk              $81     $40
;    untalk            $81     $5f
;=====================================================
;    retrieve s.a.     $82     s.a.
;    output to drive   $83     data
;    output from drive $84     data
;    invalid       $80,$85 ... $8f
;
;*****************************************************
;
tstatn=*
        lda  tedioa     ; load again
        cmp  tedioa     ; debounce the hell out of it !
        beq  tstok      ; br, ok
        jmp  idle       ; nope invalid cmd
tstok   and  #$0f       ; 16 cmds
        asl  a          ; acc*2
        tay
        lda  fnctbl-2,y         ; function table of
        sta  t0         ; jump addresses
        lda  fnctbl-1,y
        sta  t1
        lda  portc
        and  #$f7
        sta  portc      ; drop rdy low to tell ted we got it
        jmp  (t0)
;
;
        .word    invld  ; invalid cmd
;
fnctbl  .word    list   ; state chg cmd
	.word    tksa   ; talk secondary address
	.word    ciout  ; accept a byte
	.word    acptr  ; send host a byte
;
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
	.word    invld  ; invalid cmd
;
invld   lda  portc
        ora  #8
        sta  portc      ; restore rdy
        jmp  idle       ; return to idle