130 lines
2.3 KiB
ArmAsm
130 lines
2.3 KiB
ArmAsm
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//
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// Tape (turbo) part of the LOAD routine
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//
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// Based on routine by enthusi/Onslaught, found here:
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// - https://codebase64.pokefinder.org/doku.php?id=base:turbotape_loader_source
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#if CONFIG_TAPE_TURBO
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load_tape_turbo:
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jsr tape_ditch_verify // only LOAD is supported, no VERIFY
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ldy #$00
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sty PRTY // initial checksum value
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sty CIA2_TIMAHI
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lda #$FE // timer threshold for TurboTape
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sta CIA2_TIMALO
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jsr tape_ask_play
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// Read file header
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ldy #$00
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jsr tape_turbo_sync // .X gets set to 0
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stx STAL+0 // instead of a later lda, sta
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jsr tape_turbo_get_byte // important trick - save time/bytes by using y-indexing
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tay
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!:
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jsr tape_turbo_get_byte
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sta STAL+1,x // .X still 0
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inx
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cpx #$03
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bne !-
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// Read file payload
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jsr tape_turbo_sync // .X gets set to 0
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// FALLTROUGH
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load_tape_turbo_loop:
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jsr tape_turbo_get_byte
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dec CPU_R6510 // to load below i/o area!
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sta (STAL),y
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eor PRTY
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sta PRTY
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inc CPU_R6510
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iny
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bne !+
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inc STAL+1
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!:
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cpy MEMUSS+0
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lda STAL+1
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sbc MEMUSS+1
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bcc load_tape_turbo_loop
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// Verify the checksum
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jsr tape_turbo_get_byte
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cmp PRTY
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beq_far tape_load_success
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jmp tape_load_error
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tape_turbo_get_byte:
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lda #$01
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sta ROPRTY // init the to-be-read byte with 1
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!:
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jsr tape_turbo_get_bit
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rol ROPRTY
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bcc !- // is the initial 1 shifted into carry already?
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lda ROPRTY // much nicer than ldx #8: dex: loop
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rts
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tape_turbo_get_bit:
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lda #$10
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!:
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bit CIA2_ICR
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beq !- // busy loop to detect signal
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lda CIA2_ICR
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pha
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lda #$19
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sta CIA2_CRA
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pla
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sta VIC_EXTCOL // use bitvalue as d020 effect (I love that one)
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lsr
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rts
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tape_turbo_sync:
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jsr tape_turbo_get_bit
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rol ROPRTY
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lda ROPRTY
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cmp #$02
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bne tape_turbo_sync
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ldx #$09 // 9,8,... is real turboTape
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!: // I sometimes used 8,7,6... to avoid it being listed in vice :)
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jsr tape_turbo_get_byte
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cmp #$02
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beq !-
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!:
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cpx ROPRTY
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bne tape_turbo_sync
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jsr tape_turbo_get_byte
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dex
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bne !-
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rts
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#endif // CONFIG_TAPE_TURBO
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