127 lines
2.3 KiB
ArmAsm
127 lines
2.3 KiB
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 - reading speed calibration
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//
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// Needs pulse length in .A
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//
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#if CONFIG_TAPE_NORMAL
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tape_normal_calibrate_during_pilot: // reecalibration during the pilot
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sta __normal_time_S
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// We do not have any recent medium pulse measurement,
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// probably the only solution is to estimate it
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lda #$FF
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sec
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sbc __normal_time_S
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// We now have a difference from the starting point ($FF)
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clc
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ror
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sta __normal_time_M // this is temporary only!
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// We now have half the difference, substract it from
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// short pulse measurement result
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lda __normal_time_S
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sec
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sbc __normal_time_M
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// Add a small correction to gain $7D if starting from $A5. Dirty, ugly,
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// and imprecise hack - but in real life should be good enough
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clc
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adc #$05
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sta __normal_time_M // estimated medium pulse length
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jmp tape_normal_calibrate_common
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tape_normal_calibrate_after_S: // recalibration after short pulse
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sta __normal_time_S
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rts
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skip_2_bytes_trash_nvz
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// FALLTROUGH
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tape_normal_calibrate_after_M: // recalibration after medium pulse
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sta __normal_time_M
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// FALLTROUGH
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tape_normal_calibrate_common:
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// Now compare results with current threshold
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lda __normal_time_S
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sec
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sbc __pulse_threshold
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clc
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adc __normal_time_M
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cmp __pulse_threshold
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beq tape_normal_calibrate_done // branch if no recalibration needed
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// Correct the thresholds (default is $91 for the S/M one)
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bcs tape_normal_calibrate_threshold_inc // branch if .A >= memory
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// FALLTROUGH
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tape_normal_calibrate_threshold_dec:
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lda __pulse_threshold
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cmp #($91-10)
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bcc tape_normal_calibrate_done // do not decrement thresholds too far
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sec
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sbc #$02
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sta __pulse_threshold
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lda __pulse_threshold_ML
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sec
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sbc #$03
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sta __pulse_threshold_ML
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bne tape_normal_calibrate_done // branch always
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tape_normal_calibrate_threshold_inc:
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lda __pulse_threshold
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cmp #($91+11)
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bcs tape_normal_calibrate_done // do not increment thresholds too far
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clc
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adc #$02
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sta __pulse_threshold
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lda __pulse_threshold_ML
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clc
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adc #$03
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sta __pulse_threshold_ML
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// FALLTROUGH
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tape_normal_calibrate_done:
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rts
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#endif
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