111 lines
2.2 KiB
ArmAsm
111 lines
2.2 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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// XXX use calibration bits to improve reading
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// XXX find out how to use B0 tape timing
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// XXX put header type into (TAPE1)
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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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lda #$00
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sta CIA2_TIMAHI // $DD05
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lda #$FE // timer threshold for TurboTape
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sta CIA2_TIMALO // $DD04
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// Prepare for sound effects
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jsr tape_clean_sid
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// Start playing
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jsr tape_ask_play
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// FALLTROUGH
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load_tape_turbo_header:
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// Read file header; structure described here:
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// - https://www.luigidifraia.com/c64/docs/tapeloaders.html#turbotape64
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//
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// 1 byte (skipped) - file type (0 = data, odd value = relocatable, even value = non-relocatable)
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// 2 bytes - start address
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// 2 bytes - end address + 1
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// 1 byte - if $B0 (tape timing) contained at the time of saving
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// (we skip this one to match normal system header)
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// 16 bytes - filename, padded with 0x20
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jsr tape_turbo_sync_header
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ldy #$01 // to match original ROM header layout
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// FALLTROUGH
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load_tape_turbo_header_loop:
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jsr tape_turbo_get_byte
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sta (TAPE1), y
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iny
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cpy #$05
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bne !+
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jsr tape_turbo_get_byte // tape timing - skip this XXX how to use it?
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!:
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cpy #$15
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bne load_tape_turbo_header_loop
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// Handle the header
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jsr tape_clean_sid
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jsr tape_handle_header
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bcs load_tape_turbo_header // if name does not match, look for other header
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// FALLTROUGH
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load_tape_turbo_payload:
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// Initial checksum value
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lda #$00
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sta PRTY
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// Read file payload
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jsr tape_turbo_sync_payload
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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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sta (MEMUSS),y
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eor PRTY // handle checksum
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sta PRTY
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// Advance MEMUSS (see Mapping the C64, page 36)
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jsr lvs_advance_MEMUSS_check_EAL
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bne load_tape_turbo_loop
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// Get the checksum
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jsr tape_turbo_get_byte
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tax
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// Silence audio
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jsr tape_clean_sid
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// Verify the checksum
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cpx PRTY
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beq_far tape_load_success
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jmp tape_load_error
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#endif // CONFIG_TAPE_TURBO
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