work towards tape speed calibration in normal system load

c64/aliases/,aliases_ram_lowmem.s

@@ -1,6 +1,6 @@
 //
 // Names of ZP and low memory locations:
-// - Compute's Mapping the Commodore 64
+// - Computes Mapping the Commodore 64
 // - https://www.c64-wiki.com/wiki/Zeropage
 // - http://unusedino.de/ec64/technical/project64/memory_maps.html
 //
@@ -83,8 +83,8 @@
 	//
 	
 	.label IOSTATUS  = $90
-	.label STKEY     = $91  //          Keys down clears bits. STOP - bit 7, C= - bit 6, SPACE - bit 4, CTRL - bit 2
+	.label STKEY     = $91  //          keys down clears bits. STOP - bit 7, C= - bit 6, SPACE - bit 4, CTRL - bit 2
-	.label SVXT      = $92  //          -- NOT IMPLEMENTED --
+	.label SVXT      = $92  //          tape reading constant [!] our tape routines use it differently
 	.label VERCKK    = $93  //          0 = LOAD, 1 = VERIFY
 	.label C3PO      = $94  //          flag - is BSOUR content valid
 	.label BSOUR     = $95  //          serial bus buffered output byte
@@ -118,8 +118,8 @@
 	.label RIDDATA   = $AA  //          -- NOT IMPLEMENTED --
 	.label RIPRTY    = $AB  //          -- WIP -- checksum while reading tape
 #endif
-	.label SAL       = $AC  // $AC-$AD  -- NOT IMPLEMENTED -- (implemented screen part)
+	.label SAL       = $AC  // $AC-$AD  -- XXX: describe -- (implemented screen part)
-	.label EAL       = $AE  // $AE-$AF  -- NOT IMPLEMENTED -- [!] used also by screen editor, for temporary color storage when scrolling
+	.label EAL       = $AE  // $AE-$AF  -- XXX: describe -- [!] used also by screen editor, for temporary color storage when scrolling
 	.label CMP0      = $B0  // $B0-$B1  temporary tape storage, [!] here used for BRK instruction address
 	.label TAPE1     = $B2  // $B2-$B3  tape buffer pointer
 #if !CONFIG_LEGACY_SCNKEY
@@ -227,7 +227,7 @@
 #if CONFIG_MEMORY_MODEL_60K
 
 	// IRQs are disabled when doing such accesses, and a default NMI handler only increments
-	// a counter, so that if an NMI occurs, it doesn't crash the machine, but can be captured.
+	// a counter, so that if an NMI occurs, it does not crash the machine, but can be captured.
 
 	.label missed_nmi_flag  = $2A7
 	.label tiny_nmi_handler = $2A8
@@ -288,3 +288,21 @@
 #endif
 
 	//                 $3FC     $3FC-$3FF  -- UNUSED --          free for user software
+
+
+//
+// Definitions foor tape functionality
+//
+
+#if CONFIG_TAPE_NORMAL || CONFIG_TAPE_TURBO
+
+	.label __normal_time_S       = IRQTMP+0           // duration of the short pulse
+	.label __normal_time_M       = IRQTMP+1           // duration of the medium pulse
+
+	.label __turbo_half_S        = IRQTMP+0           // half-duration of the short pulse
+	.label __turbo_half_L        = IRQTMP+1           // half-duration of the long pulse
+
+	.label __pulse_threshold     = SVXT               // pulse classification threshold
+	.label __pulse_threshold_ML  = SYNO               // M/L pulse classification threshold, for normal only
+
+#endif

c64/kernal/iostack/f4a5.load.s

@@ -43,19 +43,32 @@ LOAD:
 	// Check whether we support the requested device
 	lda FA
 
+
+#if !CONFIG_TAPE_AUTODETECT
+
 #if CONFIG_TAPE_NORMAL
 	cmp #$01
 	beq_16 load_tape_normal
 #endif
-
 #if CONFIG_TAPE_TURBO
 	cmp #$07
 	beq_16 load_tape_turbo
 #endif
 
+#else // CONFIG_TAPE_AUTODETECT
+
+	cmp #$01
+	beq_16 load_tape_auto
+	cmp #$07
+	beq_16 load_tape_auto
+
+#endif
+
+
 #if CONFIG_IEC
 	jsr iec_check_devnum_lvs
 	bcc_16 load_iec
 #endif
 
+
 	jmp lvs_illegal_device_number

c64/kernal/tape/load_tape_normal.s

@@ -33,37 +33,27 @@
 // (L,S) = end-of-data marker
 
 
-// XXX use pilot to calibrate reading speed
 // XXX add error correction
+// XXX implement proper takeover to turbo during sync/pilot
 
 
 #if CONFIG_TAPE_NORMAL
 
 
+#if !CONFIG_TAPE_AUTODETECT
+
 load_tape_normal:
 
 	jsr tape_ditch_verify              // only LOAD is supported, no VERIFY
 
-#if CONFIG_TAPE_AUTODETECT
-
-	// Prepare for sound effects in case of turbo takeover
-	jsr tape_clean_sid
-
-#endif
-
 	// Start playing
 	jsr tape_common_prepare_cia
 	jsr tape_ask_play
 
-#if CONFIG_TAPE_AUTODETECT
+#else
-
-	// FALLTROUGH
 
 load_tape_normal_takeover:             // entry point for turbo->normal takeover
 
-	jsr tape_common_autodetect
-	bcs_16 load_tape_turbo_takeover
-
 #endif
 
 	// Temporarily store MEMUSS in EAL
@@ -86,10 +76,10 @@ load_tape_normal_header:
 
 	// Retrieve the header
 
-	jsr tape_normal_pilot_header
+	jsr tape_normal_get_pilot_header
 	ldy #$C1                           // size limit (including checksum)
 	jsr tape_normal_get_data
-	bcs load_tape_normal_header        // unable to read block, try again
+	bcs load_tape_normal_header        // unable to read block, try again     XXX restore MEMUSS and jump to turbo detection
 
 	// Check header type
 
@@ -127,7 +117,7 @@ load_tape_normal_payload:
 
 	// Retrieve data
 
-	jsr tape_normal_pilot_data
+	jsr tape_normal_get_pilot_data
 	ldy #$00                           // no data size limit
 	jsr tape_normal_get_data
 	bcs_16 tape_load_error

c64/kernal/tape/load_tape_turbo.s

@@ -14,8 +14,16 @@
 #if CONFIG_TAPE_TURBO
 
 
+#if !CONFIG_TAPE_AUTODETECT
+
 load_tape_turbo:
 
+#else
+
+load_tape_auto:
+
+#endif
+
 	jsr tape_ditch_verify              // only LOAD is supported, no VERIFY
 
 	// Prepare for sound effects

c64/kernal/tape/tape_common_autodetect.s

@@ -38,13 +38,13 @@ tape_common_autodetect_retry:
 	sta XSAV
 
 	ldy #$60                           // $60 pulses cover 12 bytes of turbo recording
-	jsr tape_normal_get_pulse          // first pulse might be a garbage, ignore it
+	jsr tape_common_get_pulse          // first pulse might be a garbage, ignore it
 
 	// FALLTROUGH
 
 tape_common_autodetect_loop:
 
-	jsr tape_normal_get_pulse          // read pulse for detection attempt
+	jsr tape_common_get_pulse          // read pulse for detection attempt
 	
 	// If garbage found, retry detection
 	cmp #$28

c64/kernal/tape/tape_common_get_pulse.s

@@ -0,0 +1,33 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Tape helper routine - pulse reading
+//
+// Returns pulse length (with a bias, see comments) in .A
+//
+
+
+#if CONFIG_TAPE_NORMAL || CONFIG_TAPE_TURBO
+
+
+tape_common_get_pulse:
+
+	// Contrary to original ROM implementation we do not use interrupts
+	// (see http://unusedino.de/ec64/technical/formats/tap.html) - busy wait
+	// implementation is probably just shorter
+
+	lda #$10
+!:
+	bit CIA1_ICR    // $DC0D
+	beq !-                             // busy loop to detect signal, restart timer afterwards
+	lda CIA2_TIMBLO // $DD06
+	ldx #%01010001                     // start timer, force latch reload, count timer A underflows
+	stx CIA2_CRB    // $DD0F
+
+	cmp __pulse_threshold              // sdefault pulse check
+	rts
+
+
+#endif

c64/kernal/tape/tape_common_prepare_cia.s

@@ -7,7 +7,7 @@
 //
 
 //
-// Checked under VICE, PAL, average of 256 pulses:  XXX retry measurements for NORMAL, something is probably wrong
+// Checked under VICE, PAL, average of 256 pulses:
 //
 //     normal - short  - timer goes down to $A5
 //     normal - medium - timer goes down to $7D

c64/kernal/tape/tape_normal_calibrate.s

@@ -0,0 +1,86 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Tape (normal) helper routine - reading speed calibration
+//
+// Needs pulse length in .A
+//
+
+
+#if CONFIG_TAPE_NORMAL
+
+
+tape_normal_calibrate_during_pilot:    // reecalibration during the pilot
+
+	sta __normal_time_S
+
+	// We do not have any recent medium pulse measurement,
+	// probably the only solution is to estimate it
+
+	lda $FF
+	sec
+	sbc __normal_time_S
+
+	// We now have a difference from the starting point ($FF)
+
+	clc
+	rol
+	sta __normal_time_M                // this is temporary only!
+
+	// We now have half the difference, substract it from
+	// short pulse measurement result
+
+	lda __normal_time_S
+	clc
+	sbc __normal_time_M
+
+	// XXX add some constant to get a proper __normal_time_M ($7D if starting from $A5), afterwards remove __normal_time_M initialization from tape_normal_get_pilot_header
+
+	sta __normal_time_M
+
+	jmp tape_normal_calibrate_common
+
+
+tape_normal_calibrate_after_S:         // recalibration after short pulse
+
+	sta __normal_time_S
+	rts
+	skip_2_bytes_trash_nvz
+
+	// FALLTROUGH
+
+tape_normal_calibrate_after_M:         // recalibration after medium pulse
+
+	sta __normal_time_M
+
+	// FALLTROUGH
+
+tape_normal_calibrate_common:
+
+	// Now compare results with current threshold
+
+	lda __normal_time_S
+	sec
+	sbc __pulse_threshold
+	clc
+	adc __normal_time_M
+
+	cmp __pulse_threshold
+	beq tape_normal_calibrate_done     // branch if no recalibration needed
+
+
+
+	// XXX implement recalibration
+
+
+
+
+
+tape_normal_calibrate_done:
+
+	rts
+
+
+#endif

c64/kernal/tape/tape_normal_get_bit.s

@@ -16,17 +16,20 @@ tape_normal_get_bit:
 
 	// Fetch the first pulse
 
-	jsr tape_normal_get_pulse
+	jsr tape_common_get_pulse
 	bcc tape_normal_get_bit_1
 
 	// First impulse was short, second should be medium
 
-	jsr tape_normal_get_pulse
+	jsr tape_normal_calibrate_after_S
+
+	jsr tape_common_get_pulse
 	bcs tape_normal_get_bit_error
 
+	jsr tape_normal_calibrate_after_M
+
 	// We have a bit '0'
 
-	// Carry flag already clear
 	lda #$00
 
 	// FALLTROUGH
@@ -34,6 +37,7 @@ tape_normal_get_bit:
 tape_normal_get_bit_done:
 
 	sta VIC_EXTCOL
+	clc
 	rts
 
 
@@ -41,9 +45,13 @@ tape_normal_get_bit_1:
 
 	// First impulse was medium, second should be short
 
-	jsr tape_normal_get_pulse
+	jsr tape_normal_calibrate_after_M
+
+	jsr tape_common_get_pulse
 	bcc tape_normal_get_bit_error
 
+	jsr tape_normal_calibrate_after_S
+
 	// We have a bit '1'
 
 	clc

c64/kernal/tape/tape_normal_get_marker.s

@@ -5,22 +5,49 @@
 //
 // Tape (normal) helper routine - marker reading
 //
-// Reeturns marker type in Carry flag, set = end of data
+// Reeturns marker type in Carry flag, set = end of data (normal marker) or failure (marker while sync)
 //
 
 
 #if CONFIG_TAPE_NORMAL
 
+	// (L,M) - end of byte, (L,S) - end of data
 
-tape_normal_get_marker:
+
+tape_normal_get_marker: 
+
+
+	jsr tape_common_get_pulse
+	cmp __pulse_threshold_ML
+	bcs tape_normal_get_marker                             // too short for a long pulse
+
+	// FALLTROUGH
+
+tape_normal_get_marker_type:
+
+	jmp tape_common_get_pulse
+
+
+
+!:  // Not an entry point!!!
+
+	// XXX check for short pulses of turbo here
+
+	jsr tape_normal_calibrate_during_pilot                 // while sync use short pulses for calibration
+
+	// FALLTROUGH
+
+tape_normal_get_marker_while_sync:
 
 	// (L,M) - end of byte, (L,S) - end of data
 
-	jsr tape_normal_get_pulse
+	jsr tape_common_get_pulse
-	cmp #($FF - $98 - $04)
+	bcs !-                                                 // branch if short pulse
-	bcs tape_normal_get_marker                             // too short for a long pulse
 
-	jmp tape_normal_get_pulse
+	cmp __pulse_threshold_ML
+	bcs tape_normal_get_marker_while_sync                  // too short for a long pulse
+	
+	bcc tape_normal_get_marker_type                        // branch always
 
 
 #endif

c64/kernal/tape/tape_normal_get_pilot.s

@@ -0,0 +1,93 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Tape (turbo) helper routine - handling the pilot
+//
+
+// Injest the pilot - series of short pulses. According to http://sidpreservation.6581.org/tape-format/
+// it consist of the following number of pulses:
+// - $6A00 for header
+// - $1A00 for data and seq block header
+// - $4F for repeated header/data
+
+
+#if CONFIG_TAPE_NORMAL
+
+
+// XXX in tape_normal_get_pilot_header also try to detect turbo
+
+tape_normal_get_pilot_header:          // entry point, reset calibration, require 128x $40 pulses
+
+	// Reading the pilot header is the first action performed,
+	// thus start by setting default timings, as measured during
+	// VICE test
+
+	lda #$7D
+	sta __normal_time_M                // __normal_time_S will be set within the pilot
+	lda #$91
+	sta __pulse_threshold
+	lda #$67
+	sta __pulse_threshold_ML
+
+	lda #$80
+
+	skip_2_bytes_trash_nvz
+
+	// FALLTROUGH
+
+tape_normal_get_pilot_data:            // entry point, require 4x $40 pulses
+
+	lda #$04
+
+	skip_2_bytes_trash_nvz
+
+	// FALLTROUGH
+
+tape_normal_get_pilot_short:           // entry point, require 1x $40 pulses
+
+	lda #$01
+
+	// FALLTROUGH
+
+tape_normal_get_pilot_common:
+
+	sta FSBLK
+
+	lda #$0B
+	sta VIC_EXTCOL
+
+	// FALLTROUGH
+
+tape_normal_get_pilot_common_restart:
+
+	lda FSBLK
+	sta ROPRTY
+
+	// FALLTROUGH
+
+tape_normal_get_pilot_common_loop_outer:
+
+	ldy #$40
+
+	// FALLTROUGH
+
+tape_normal_get_pilot_common_loop_inner:
+
+	jsr tape_common_get_pulse
+	// XXX check for short pulses of turbo here
+	bcc tape_normal_get_pilot_common_restart     // not a pilot - try again
+	
+	jsr tape_normal_calibrate_during_pilot
+
+	dey
+	bne tape_normal_get_pilot_common_loop_inner
+
+	dec ROPRTY
+	bne tape_normal_get_pilot_common_loop_outer
+
+	rts
+
+
+#endif

c64/kernal/tape/tape_normal_get_pulse.s

@@ -1,44 +0,0 @@
-// #LAYOUT# STD *        #TAKE
-// #LAYOUT# *   KERNAL_0 #TAKE
-// #LAYOUT# *   *        #IGNORE
-
-//
-// Tape (normal) helper routine - pulse reading
-//
-// Returns pulse length (with a bias, see comments) in .A
-//
-
-
-#if CONFIG_TAPE_NORMAL
-
-
-tape_normal_get_pulse:
-
-	// Contrary to original ROM implementation we do not use interrupts
-	// (see http://unusedino.de/ec64/technical/formats/tap.html) - busy wait
-	// implementation is probably just shorter
-
-	lda #$10
-!:
-	bit CIA1_ICR    // $DC0D
-	beq !-                             // busy loop to detect signal, restart timer afterwards
-	lda CIA2_TIMBLO // $DD06
-	ldx #%01010001                     // start timer, force latch reload, count timer A underflows
-	stx CIA2_CRB    // $DD0F
-
-	// Since the signal appeared to the point of timer restart we used:
-	// bit - 4 cycles
-	// beq - 2 cycles
-	// lda - 4 cycles
-	// ldx - 2 cycles
-	// stx - 4 cycles
-	// plus average 3 cycles (bit + beq time divided by 2) from value change to 'bit' instruction
-	// minus average 2 cycles due to timer A running continouslyy (might start before the pulse)
-	// this is total 17 cycles, or $4 periods of 4 ticks (timer A) each - we need to take it into account
-	// every time we check the pulse length
-
-	cmp #($FF - $72 - $04)            // short vs medium is the default check
-	rts
-
-
-#endif

c64/kernal/tape/tape_normal_pilot.s

@@ -1,78 +0,0 @@
-// #LAYOUT# STD *        #TAKE
-// #LAYOUT# *   KERNAL_0 #TAKE
-// #LAYOUT# *   *        #IGNORE
-
-//
-// Tape (turbo) helper routine - handling the pilot
-//
-
-// Injest the pilot - series of short pulses. According to http://sidpreservation.6581.org/tape-format/
-// it consist of the following number of pulses:
-// - $6A00 for header
-// - $1A00 for data and seq block header
-// - $4F for repeated header/data
-
-
-#if CONFIG_TAPE_NORMAL
-
-
-
-tape_normal_pilot_short: // require 1x $40 pulses
-
-	lda #$01
-
-	// FALLTROUGH
-
-tape_normal_pilot_common:
-
-	sta FSBLK
-
-	// FALLTROUGH
-
-tape_normal_pilot_common_restart:
-
-	lda #$0B
-	sta VIC_EXTCOL
-
-	lda FSBLK
-	sta ROPRTY
-
-	// FALLTROUGH
-
-tape_normal_pilot_common_loop_outer:
-
-	ldy #$40
-
-	// FALLTROUGH
-
-tape_normal_pilot_common_loop_inner:
-
-	jsr tape_normal_get_pulse
-	bcc tape_normal_pilot_common_restart         // not a pilot - try again
-
-	dey
-	bne tape_normal_pilot_common_loop_inner
-
-	dec ROPRTY
-	bne tape_normal_pilot_common_loop_outer
-
-	rts
-
-
-
-tape_normal_pilot_data: // require 4x $40 pulses
-
-	lda #$04
-
-	skip_2_bytes_trash_nvz
-
-	// FALLTROUGH
-
-tape_normal_pilot_header: // require 128x $40 pulses
-
-	lda #$80
-
-	jmp tape_normal_pilot_common    // XXX calibrate tape speed afterwards
-
-
-#endif

c64/kernal/tape/tape_normal_sync.s

@@ -19,7 +19,7 @@ tape_normal_sync:
 
 	// Injest bytes of decreasing values
 
-	jsr tape_normal_get_marker
+	jsr tape_normal_get_marker_while_sync
 	bcs tape_normal_sync_fail          // branch if end of data marker
 	
 	jsr tape_normal_get_byte

c64/kernal/tape/tape_turbo_get_bit.s

@@ -14,29 +14,13 @@
 
 
 tape_turbo_get_bit:
-
-#if CONFIG_TAPE_NORMAL
 	
-	jsr tape_normal_get_pulse          // reuse routine from NORMAL system
+	jsr tape_common_get_pulse
-
-#else
-
-	lda #$10
-!:
-	bit CIA1_ICR    // $DC0D
-	beq !-                             // busy loop to detect signal, restart timer afterwards
-	lda CIA2_TIMBLO // $DD06
-	ldx #%01010001                     // start timer, force latch reload, count timer A underflows
-	stx CIA2_CRB    // $DD0F
-
-#endif
-
-	cmp SYNO                           // threshold
 	bcs !+
 
 	clc
 	ror
-	sta IRQTMP+0                       // store half of the last measurement result for short pulse
+	sta __turbo_half_S                 // store half of the last measurement result for short pulse
 
 	lda #$01
 	sta SID_SIGVOL
@@ -47,7 +31,7 @@ tape_turbo_get_bit:
 !:
 	clc
 	ror
-	sta IRQTMP+1                       // store half of the last measurement result for long pulse
+	sta __turbo_half_L                 // store half of the last measurement result for long pulse
 
 	lda #$00
 	sta SID_SIGVOL

c64/kernal/tape/tape_turbo_get_byte.s

@@ -28,28 +28,28 @@ tape_turbo_get_byte:
 
 	// Compensate for tape speed variations
 
-	lda IRQTMP+0                       // half of the last value for bit '0'
+	lda __turbo_half_S                 // half of the last value for bit '0'
 	clc
-	adc IRQTMP+1                       // half of the last value for bit '1'
+	adc __turbo_half_L                 // half of the last value for bit '1'
 	
 	sec
-	sbc SYNO                           // now we have a diff between current threshold and calculated one
+	sbc __pulse_threshold              // now we have a diff between current threshold and calculated one
 	beq tape_turbo_get_byte_done       // branch if threshold correction not needed
 
 	bpl !+
 
-	lda SYNO
+	lda __pulse_threshold
 	cmp #($BF - 10)
 	beq tape_turbo_get_byte_done       // do not decrease threshold too far no matter what
 
-	dec SYNO
+	dec __pulse_threshold
 	bne tape_turbo_get_byte_done       // branch always
 !:
-	lda SYNO
+	lda __pulse_threshold
 	cmp #($BF + 10)
 	beq tape_turbo_get_byte_done       // do not increase threshold too far no matter what
 
-	inc SYNO
+	inc __pulse_threshold
 
 tape_turbo_get_byte_done:
 

c64/kernal/tape/tape_turbo_sync.s

@@ -17,7 +17,7 @@ tape_turbo_sync_header:
 
 	// Initial pulse threshold
 	lda #$BF                           // measured 128 bits '0' and 128 bits '1' under VICE, calculated average
-	sta SYNO
+	sta __pulse_threshold
 
 	// Synchronize with start of sync sequence
 	jsr tape_turbo_sync_first