94 lines
1.7 KiB
ArmAsm
94 lines
1.7 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 (turbo) helper routine - handling the pilot
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//
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// Injest the pilot - series of short pulses. According to http://sidpreservation.6581.org/tape-format/
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// it consist of the following number of pulses:
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// - $6A00 for header
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// - $1A00 for data and seq block header
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// - $4F for repeated header/data
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#if CONFIG_TAPE_NORMAL
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tape_normal_get_pilot_header: // entry point, reset calibration, require 128x $40 pulses
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// Reading the pilot header is the first action performed,
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// thus start by setting default thresholds
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lda #$91
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sta __pulse_threshold
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lda #$67
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sta __pulse_threshold_ML
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lda #$80
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skip_2_bytes_trash_nvz
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// FALLTROUGH
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tape_normal_get_pilot_data: // entry point, require 4x $40 pulses
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lda #$04
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skip_2_bytes_trash_nvz
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// FALLTROUGH
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tape_normal_get_pilot_short: // entry point, require 1x $40 pulses
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lda #$01
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// FALLTROUGH
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tape_normal_get_pilot_common:
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sta FSBLK
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lda #$0B
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sta VIC_EXTCOL
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// FALLTROUGH
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tape_normal_get_pilot_common_restart:
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lda FSBLK
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sta ROPRTY
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// FALLTROUGH
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tape_normal_get_pilot_common_loop_outer:
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ldy #$40
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// FALLTROUGH
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tape_normal_get_pilot_common_loop_inner:
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jsr tape_common_get_pulse
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bcc tape_normal_get_pilot_common_restart // not a pilot - try again
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#if CONFIG_TAPE_AUTODETECT
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// Try to distinguish turbo by cheecking for short signals
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cmp #$B9 // see comment in tape_common_autodetect.s
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bcs !+
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#endif
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jsr tape_normal_calibrate_during_pilot
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dey
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bne tape_normal_get_pilot_common_loop_inner
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dec ROPRTY
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bne tape_normal_get_pilot_common_loop_outer
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clc
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!:
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rts
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#endif
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