118 lines
2.0 KiB
ArmAsm
118 lines
2.0 KiB
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# * KERNAL_0 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Tape (normal) helper routine - data block (primary) reading
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//
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// Stores data starting from MEMUSS, Carry set means error, on 0 bit .A is 0 too
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// .Y not equal to 0 - returns error if data block is longer (length includes checksum)
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// XXX improve error handling - do not ignore second copy, handle damaged sync part
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#if CONFIG_TAPE_NORMAL
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tape_normal_get_data_1:
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// Initialize checksum (RIPRTY, see http://sta.c64.org/cbm64mem.html)
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// and pointers for error log and correction mechanism
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lda #$00
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sta RIPRTY
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#if !CONFIG_TAPE_NO_ERROR_CORRECTION
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sta PTR1
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sta PTR2
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#endif
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// FALLTROUGH
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tape_normal_get_data_1_block:
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//
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// Read the 1st copy of the block
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//
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// Read sync of the block
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ldy #$89
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jsr tape_normal_sync
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bcs tape_normal_get_data_1_fail
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jsr tape_normal_get_marker
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tape_normal_get_data_1_loop:
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jsr tape_normal_get_byte
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bcc tape_normal_get_data_1_loop_byte_OK
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#if CONFIG_TAPE_NO_ERROR_CORRECTION
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bcs tape_normal_get_data_1_fail
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#else
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// Problem reading a byte, try to add it to the error log
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tsx
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cpx #$20 // just to be on a safe side
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bcc tape_normal_get_data_1_fail // branch if no more space in error log
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ldx PTR1
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lda MEMUSS+0
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sta STACK, x
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inx
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lda MEMUSS+1
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sta STACK, x
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inx
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stx PTR1
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// Addres added to error log, check if this was a checksum
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jsr tape_normal_get_marker
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bcc tape_normal_get_data_1_loop_advance
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bcs tape_normal_get_data_1_success
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#endif
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tape_normal_get_data_1_loop_byte_OK:
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jsr tape_normal_get_marker
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bcc !+
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// End of the block
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jsr tape_normal_update_checksum
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jmp tape_normal_get_data_1_success
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!:
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// Store byte, calculate checksum
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lda INBIT
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ldy #$00
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sta (MEMUSS), y
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jsr tape_normal_update_checksum
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// FALLTROUGH
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tape_normal_get_data_1_loop_advance:
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// Advance pointer
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#if !HAS_OPCODES_65CE02
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jsr lvs_advance_MEMUSS
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#else
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inw MEMUSS+0
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#endif
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jmp tape_normal_get_data_1_loop
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tape_normal_get_data_1_success:
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clc
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rts
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tape_normal_get_data_1_fail:
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sec
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rts
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#endif
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