69 lines
1017 B
ArmAsm
69 lines
1017 B
ArmAsm
// #LAYOUT# STD * #TAKE
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// #LAYOUT# M65 KERNAL_1 #TAKE
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// #LAYOUT# * * #IGNORE
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//
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// Tape (normal) helper routine - bit reading
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//
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// Returns bit in Zero flag, Carry set means error, on 0 bit .A is 0 too
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//
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#if CONFIG_TAPE_NORMAL
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tape_normal_get_bit:
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// Fetch the first pulse
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jsr tape_common_get_pulse
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bcc tape_normal_get_bit_1
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// First impulse was short, second should be medium
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jsr tape_normal_calibrate_after_S
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jsr tape_common_get_pulse
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bcs tape_normal_get_bit_error
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jsr tape_normal_calibrate_after_M
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// We have a bit '0'
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lda #$00
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// FALLTROUGH
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tape_normal_get_bit_done:
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sta VIC_EXTCOL
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clc
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rts
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tape_normal_get_bit_1:
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// First impulse was medium, second should be short
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jsr tape_normal_calibrate_after_M
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jsr tape_common_get_pulse
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bcc tape_normal_get_bit_error
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jsr tape_normal_calibrate_after_S
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// We have a bit '1'
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clc
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lda #$06
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bne tape_normal_get_bit_done // branch always
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tape_normal_get_bit_error:
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sec
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rts
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#endif // CONFIG_TAPE_NORMAL
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