byte decoding for normal tape finished

c64/kernal/tape/load_tape_normal.s

@@ -50,9 +50,6 @@ load_tape_normal:
 
 	ldx #%00010001                     // start timer, force latch reload
 	stx CIA2_CRA  // $DD0E
-
-	// Prepare for sound effects
-	jsr tape_clean_sid                 // XXX implement some effects
 	
 	// Start playing
 	jsr tape_ask_play

c64/kernal/tape/tape_normal_get_bit.s

@@ -2,7 +2,7 @@
 //
 // Tape (turbo) helper routine - bit reading
 //
-// Returns bit in Zero flag, Carry set means error
+// Returns bit in Zero flag, Carry set means error, on 0 bit .A is 0 too
 //
 
 
@@ -23,7 +23,7 @@ tape_normal_get_bit:
 
 	// We have a bit '1'
 
-	clc
+	// Carry flag already clear
 	lda #$06
 
 	// FALLTROUGH
@@ -43,13 +43,12 @@ tape_normal_get_bit_0:
 
 	// We have a bit '0'
 
-	// Carry flag already clear
+	clc
 	lda #$00
 	beq tape_normal_get_bit_done       // branch always
 
 
 tape_normal_get_bit_error:
-
 	sec
 	rts
 

c64/kernal/tape/tape_normal_get_byte.s

@@ -2,7 +2,7 @@
 //
 // Tape (turbo) helper routine - byte reading
 //
-// Returns byte in .A
+// Returns byte in .A, Carry flag set = error
 //
 
 
@@ -11,11 +11,13 @@
 
 tape_normal_get_byte:
 
-	lda #$0B
-	sta VIC_EXTCOL
+	// Init byte checksum and canary bit
+	lda #$01
+	sta ROPRTY
+	lda #%01111111                     // canary bit is 0
+	pha
 
 	// First we need a byte marker - (L,M)
-
 !:
 	jsr tape_normal_get_pulse
 	cmp #($100 - $95 - $05)
@@ -25,25 +27,55 @@ tape_normal_get_byte:
 
 	// Now fetch individual bits
 
-	// XXX finish this
+tape_normal_get_byte_loop:
 
 	jsr tape_normal_get_bit
+	bcs tape_normal_get_byte_error
+	beq !+
+
+	// Handle parity bit
+	lda #$01
+	eor ROPRTY
+	sta ROPRTY
+
+	sec
+!:                                     // moved bit state from Zero to Carry flag
+
+	pla
+	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
+
 	jsr tape_normal_get_bit
-	jsr tape_normal_get_bit
-	jsr tape_normal_get_bit
-	jsr tape_normal_get_bit
-	jsr tape_normal_get_bit
-	jsr tape_normal_get_bit
-	jsr tape_normal_get_bit
-
-
-
-
+	bcs tape_normal_get_byte_error
+	beq !+
+	lda #$01
+!:
+	eor ROPRTY
+	beq tape_normal_get_byte_error
 
+	// Checksum validated succesfully
+	
+	ldx #$0B
+	// Carry already clear
 
+	// FALLTROUGH
 
+tape_normal_get_byte_done:
 
+	pla
+	stx VIC_EXTCOL
 	rts
 
 
+tape_normal_get_byte_error:
+
+	ldx #$09
+	sec                                // make sure Carry is set to indicate error
+	bcs tape_normal_get_byte_done
+
+
 #endif