updated documentation, added synchronization and pilot support to tape load

CONTRIBUTORS.md

@@ -1,2 +1,3 @@
 
-Although the project itself is LGPL3, I (FeralChild64) allow to redistribute my contributions to this project under any OSI (Open Source Initiative) approved open source license.
+Although the project itself is LGPL3, I (FeralChild64 - Roman St********ski) allow to redistribute
+my contributions to this project under any OSI (Open Source Initiative) approved open source license.

Makefile

@@ -117,7 +117,7 @@ build/target_generic/OUTB.BIN     build/target_generic/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_BASIC) $(SRCDIR_BASIC) \
     c64/,,config_generic.s     build/target_generic/KERNAL_combined.sym \
     $(foreach dir,$(SRCDIR_BASIC),$(wildcard $(dir)/*.s))
-build/target_testing/OUTB.BIN     build/target_generic/BASIC_combined.vs: \
+build/target_testing/OUTB.BIN     build/target_testing/BASIC_combined.vs: \
     $(TOOL_ASSEMBLER) $(TOOL_BUILD_SEGMENT) $(GEN_BASIC) $(SRCDIR_BASIC) \
     c64/,,config_testing.s     build/target_testing/KERNAL_combined.sym \
     $(foreach dir,$(SRCDIR_BASIC),$(wildcard $(dir)/*.s))

c64/aliases/,aliases_ram_lowmem.s

@@ -111,7 +111,7 @@
 	.label TBTCNT    = $A4  //          temporary variable for tape and IEC, [!] our usage probably differs in details
 	.label CNTDN     = $A5  //          -- NOT IMPLEMENTED --
 	.label BUFPNT    = $A6  //          -- NOT IMPLEMENTED --
-	.label INBIT     = $A7  //          -- NOT IMPLEMENTED --
+	.label INBIT     = $A7  //          temporary storage for tape / RS-232 received bits
 #if !CONFIG_LEGACY_SCNKEY
 	.label BITCI     = $A8  //          -- NOT IMPLEMENTED --
 	.label RINONE    = $A9  //          -- WIP -- (UP9600 only) RS-232 check for start bit flag

c64/kernal/tape/load_tape_normal.s

@@ -28,6 +28,9 @@
 // (L,S) = end-of-data marker
 
 
+// XXX use pilot to calibrate reading speed
+
+
 #if CONFIG_TAPE_NORMAL
 
 
@@ -58,10 +61,18 @@ load_tape_normal:
 
 load_tape_normal_header:
 
-	// XXX replace this placeholder by a real routine
+	lda #$00
+	sta ROPRTY                         // initialize EOR checksum
+!:
+	jsr tape_normal_pilot
+	ldy #$89
+	jsr tape_normal_sync
+	bcs !-
 
+	// XXX replace this placeholder with a real routine
+!:
 	jsr tape_normal_get_byte
-	jmp load_tape_normal_header
+	jmp !-
 
 
 #endif

c64/kernal/tape/tape_normal_get_bit.s

@@ -14,17 +14,17 @@ tape_normal_get_bit:
 	// Fetch the first pulse
 
 	jsr tape_normal_get_pulse
-	bcc tape_normal_get_bit_0
+	bcc tape_normal_get_bit_1
 
-	// First impulse was short, second should be long
+	// First impulse was short, second should be medium
 
 	jsr tape_normal_get_pulse
 	bcs tape_normal_get_bit_error
 
-	// We have a bit '1'
+	// We have a bit '0'
 
 	// Carry flag already clear
-	lda #$06
+	lda #$00
 
 	// FALLTROUGH
 
@@ -34,21 +34,22 @@ tape_normal_get_bit_done:
 	rts
 
 
-tape_normal_get_bit_0:
+tape_normal_get_bit_1:
 
-	// First impulse was long, second should be short
+	// First impulse was medium, second should be short
 
 	jsr tape_normal_get_pulse
 	bcc tape_normal_get_bit_error
 
-	// We have a bit '0'
+	// We have a bit '1'
 
 	clc
-	lda #$00
+	lda #$06
-	beq tape_normal_get_bit_done       // branch always
+	bne tape_normal_get_bit_done       // branch always
 
 
 tape_normal_get_bit_error:
+	
 	sec
 	rts
 

c64/kernal/tape/tape_normal_get_byte.s

@@ -13,9 +13,9 @@ tape_normal_get_byte:
 
 	// Init byte checksum and canary bit
 	lda #$01
-	sta ROPRTY
+	sta PRTY
 	lda #%01111111                     // canary bit is 0
-	pha
+	sta INBIT
 
 	// First we need a byte marker - (L,M)
 !:
@@ -35,16 +35,13 @@ tape_normal_get_byte_loop:
 
 	// Handle parity bit
 	lda #$01
-	eor ROPRTY
+	eor PRTY
-	sta ROPRTY
+	sta PRTY
 
 	sec
 !:                                     // moved bit state from Zero to Carry flag
 
-	pla
+	ror INBIT                          // put the bit in
-	ror                                // put the bit in
-	pha
-
 	bcs tape_normal_get_byte_loop      // loop if no canary bit reached
 
 	// Byte retrieved (on stack), now we need to validate the checksum
@@ -54,8 +51,8 @@ tape_normal_get_byte_loop:
 	beq !+
 	lda #$01
 !:
-	eor ROPRTY
+	eor PRTY
-	beq tape_normal_get_byte_error
+	bne tape_normal_get_byte_error
 
 	// Checksum validated succesfully
 	
@@ -66,8 +63,8 @@ tape_normal_get_byte_loop:
 
 tape_normal_get_byte_done:
 
-	pla
 	stx VIC_EXTCOL
+	lda INBIT
 	rts
 
 

c64/kernal/tape/tape_normal_pilot.s

@@ -0,0 +1,29 @@
+
+//
+// Tape (turbo) helper routine - handling the pilot
+//
+
+
+#if CONFIG_TAPE_NORMAL
+
+
+tape_normal_pilot:
+
+	// Injest the pilot - series of short pulses. According to http://sidpreservation.6581.org/tape-format/
+	// it consist of the foollowing number of pulses:
+	// - $6A00 for header
+	// - $1A00 for data and seq block header
+	// - $4F for repeated header/data
+
+	ldy #$05                           // this should be enough
+!:
+	jsr tape_normal_get_pulse
+	bcc tape_normal_pilot              // not a pilot - try again
+
+	dey
+	bne !-
+
+	rts
+
+
+#endif

c64/kernal/tape/tape_normal_sync.s

@@ -0,0 +1,36 @@
+
+//
+// Tape (turbo) helper routine - synchronization handling
+//
+// .Y should contain start value (either $89 or $09)
+// Carry set = failed
+
+
+#if CONFIG_TAPE_NORMAL
+
+
+tape_normal_sync:
+
+	// Injest bytes of decreasing values
+
+	jsr tape_normal_get_byte
+	bcs tape_normal_sync_fail
+
+	cpy INBIT                          // INBIT contains same value as .A
+	bne tape_normal_sync_fail
+
+	dey
+	and #%01111110
+	bne tape_normal_sync               // branch if not $80 and not $00
+
+	clc
+	rts
+
+
+tape_normal_sync_fail:
+
+	sec
+	rts
+
+
+#endif

c64/kernal/tape/tape_turbo_get_byte.s

@@ -15,12 +15,12 @@
 tape_turbo_get_byte:
 
 	lda #$01
-	sta ROPRTY                         // init the to-be-read byte with 1 (canary bit to mark loop end)
+	sta INBIT                          // init the to-be-read byte with 1 (canary bit to mark loop end)
 !:
 	jsr tape_turbo_get_bit	
-	rol ROPRTY
+	rol INBIT
 	bcc !-	                           // is the initial 1 shifted into carry already?
-	lda ROPRTY                         // much nicer than ldx #8: dex: loop
+	lda INBIT                          // much nicer than ldx #8: dex: loop
 	
 	rts
 

c64/kernal/tape/tape_turbo_sync.s

@@ -13,8 +13,8 @@
 tape_turbo_sync_common:
 
 	jsr tape_turbo_get_bit 
-	rol ROPRTY
+	rol INBIT
-	lda ROPRTY
+	lda INBIT
 	cmp #$02
 	bne tape_turbo_sync_common
 	rts
@@ -37,14 +37,14 @@ tape_turbo_sync_payload:
 
 	jsr tape_turbo_sync_common
 !:
-	ldx #$09                           // 9,8,... is real turboTape
+	ldx #$09                           // 9, 8, ...
-!:                                     // I sometimes used 8,7,6... to avoid it being listed in vice :)
+!:
  	jsr tape_turbo_get_byte
  	cmp #$02
  	beq !-
  	ldy #$00
 !: 
-	cpx ROPRTY
+	cpx INBIT
 	bne tape_turbo_sync_payload
 	jsr tape_turbo_get_byte
 	dex