further improved turbo tape calibration sequence

c64/kernal/tape/tape_turbo_sync.s

@@ -11,17 +11,9 @@
 #if CONFIG_TAPE_TURBO
 
 
-tape_turbo_sync_common:
-
-	jsr tape_turbo_get_bit 
-	rol INBIT
-	lda INBIT
-	cmp #$02
-	bne tape_turbo_sync_common
-	rts
-
 tape_turbo_sync_header:
 
+
 #if CONFIG_TAPE_TURBO_AUTOCALIBRATE
 
 	// Initial pulse threshold
@@ -38,13 +30,19 @@ tape_turbo_sync_header:
 
 #endif // CONFIG_TAPE_TURBO_AUTOCALIBRATE
 
+	// Synchronize with start of sync sequence
+	jsr tape_turbo_sync_first
+
 	// Perform synchronization
 	ldx #$C0
 !:
 	phx_trash_a
 	ldy #$04
 !:
-	jsr tape_turbo_sync_common
+	jsr tape_turbo_get_byte
+	cmp #$02
+	bne tape_turbo_sync_header         // branch if failure
+
 	dey
 	bne !-
 	plx_trash_a
@@ -96,7 +94,7 @@ tape_turbo_sync_calibrate_loop:
 
 tape_turbo_sync_payload:
 
-	jsr tape_turbo_sync_common
+	jsr tape_turbo_sync_first
 !:
 	ldx #$09                           // 9, 8, ...
 !:

c64/kernal/tape/tape_turbo_sync_first.s

@@ -0,0 +1,24 @@
+#if ROM_LAYOUT_STD || (ROM_LAYOUT_M65 && SEGMENT_KERNAL_0)
+
+//
+// Tape (turbo) helper routine - syynchronize to first byte with value $02
+//
+
+#if CONFIG_TAPE_TURBO
+
+
+tape_turbo_sync_first:
+
+	jsr tape_turbo_get_bit 
+	rol INBIT
+	lda INBIT
+	cmp #$02
+	bne tape_turbo_sync_first
+
+	rts
+
+
+#endif
+
+
+#endif // ROM layout