169 lines
3.0 KiB
ArmAsm
169 lines
3.0 KiB
ArmAsm
;diskload8000.s
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org = $9000 ; should be $9000
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cout = $FDED ; character out sub
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crout = $FD8E ; CR out sub
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prbyte = $FDDA ; print byte in hex
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tapein = $C060 ; read tape interface
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warm = $FF69 ; back to monitor
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clear = $FC58 ; clear screen
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endbas = $80C
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target = $1000
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; zero page parameters
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begload = $00 ; begin load location LSB/MSB
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endload = $02 ; end load location LSB/MSB
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chksum = $04 ; checksum location
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pointer = $0C ; LSB/MSB pointer
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start:
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.org endbas
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move: ; end of BASIC, move code to readtape addr
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ldx #0
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move1:
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lda moved,x
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sta readtape,x
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; lda moved+256,x
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; sta readtape+256,x
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inx
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bne move1
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phase1:
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jsr crout ; print LOADING...
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lda #<loadm
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ldy #>loadm
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jsr print
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; diskload2 ORG
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lda #$D0 ; store begin location LSB
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sta begload
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lda #$96 ; store begin location MSB
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sta begload+1
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; end of DOS + 1 for comparison
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lda #$00 ; store end location LSB
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sta endload
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lda #$C0 ; store end location MSB
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sta endload+1
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jsr readtape ; get the code
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jmp $9700 ; run it
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loadm:
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.byte "LOADING INSTA-DISK, ETA "
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loadsec: ; 10 bytes for "XX SEC. ",$00
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.byte 0,0,0,0,0,0,0,0,0,0
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moved:
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.org org ; $9000
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readtape:
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lda begload ; load begin LSB location
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sta store+1 ; store it
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lda begload+1 ; load begin MSB location
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sta store+2 ; store it
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ldx #0 ; set X to 0
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lda #1 ; set A to 0
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nsync: bit tapein ; 4 cycles, sync bit ; first pulse
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bpl nsync ; 2 + 1 cycles
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main: ldy #0 ; 2 set Y to 0
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psync: bit tapein ;
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bmi psync
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ploop: iny ; 2 cycles
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bit tapein ; 4 cycles
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bpl ploop ; 2 +1 if branch, +1 if in another page
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; total ~9 cycles
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cpy #$40 ; 2 cycles if Y - $40 > 0 endcode (770Hz)
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bpl endcode ; 2(3)
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cpy #$15 ; 2 cycles if Y - $15 > 0 main (2000Hz)
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bpl main ; 2(3)
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cpy #$07 ; 2, if Y<, then clear carry, if Y>= set carry
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store: rol store+1,x ; 7, roll carry bit into store
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ldy #0 ; 2
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asl ; 2 A*=2
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bne main ; 2(3)
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lda #1 ; 2
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inx ; 2 cycles
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bne main ; 2(3)
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inc store+2 ; 6 cycles
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jmp main ; 3 cycles
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; 34 subtotal max
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; 36 subtotal max
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endcode:
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txa ; write end of file location + 1
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clc
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adc store+1
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sta store+1
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bcc endcheck ; LSB didn't roll over to zero
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inc store+2 ; did roll over to zero, inc MSB
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endcheck: ; check for match of expected length
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lda endload
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cmp store+1
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bne error
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lda endload+1
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cmp store+2
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bne error
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jsr ok
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sumcheck:
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jsr crout
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lda #<chkm
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ldy #>chkm
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jsr print
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lda #0
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sta pointer
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lda begload+1
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sta pointer+1
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lda #$ff ; init checksum
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ldy begload
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sumloop:
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eor (pointer),y
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;last page?
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ldx pointer+1
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cpx endload+1
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beq last
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iny
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bne sumloop
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inc pointer+1
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bne sumloop
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last:
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iny
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cpy endload
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bcc sumloop
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ldy #0
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eor (endload),y
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; sta chksum
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; lda chksum
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bne error
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jmp ok ; return to caller
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error:
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lda #<errm
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ldy #>errm
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jsr print
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jmp warm
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ok:
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lda #<okm
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ldy #>okm
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print:
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sta pointer
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sty pointer+1
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ldy #0
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lda (pointer),y ; load initial char
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print1: ora #$80
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jsr cout
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iny
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lda (pointer),y
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bne print1
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rts
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chkm: .asciiz "CHKSUM "
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okm: .asciiz "OK"
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errm: .asciiz "ERROR"
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end:
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