more work towards tape error correction

c64/kernal/tape/load_tape_normal.s

@@ -62,16 +62,15 @@ load_tape_normal_header:
 
 	// Try to load header into tape buffer (we will restore MEMUSS later)
 
-	lda TAPE1+1
-	sta MEMUSS+1
-	lda TAPE1+0
-	sta MEMUSS+0
-
-	// Retrieve the header
-
 	jsr tape_normal_get_pilot_header
-	jsr tape_normal_get_data
+
-	bcs load_tape_normal_header        // unable to read block, try again     XXX restore MEMUSS and jump to turbo detection
+	jsr load_tape_normal_buf_MEMUSS
+	jsr tape_normal_get_data_1
+	bcs load_tape_normal_header        // unable to read block, try again     XXX jump to turbo detection
+
+	jsr load_tape_normal_buf_MEMUSS
+	jsr tape_normal_get_data_2
+	bcs load_tape_normal_header        // block load error, try again         XXX jump to turbo detection
 
 	// Check header type
 
@@ -103,13 +102,27 @@ load_tape_normal_payload:
 
 	jsr tape_normal_get_pilot_data
 	ldy #$00                           // no data size limit
-	jsr tape_normal_get_data
+	jsr tape_normal_get_data_1
 	bcs_16 tape_load_error
 
 	jsr lvs_check_EAL
 	bne_16 tape_load_error             // amount of data read does not match header info
 
+	// XXX setup MEMUSS once again
+	jsr tape_normal_get_data_2
+	bcs_16 tape_load_error
+
 	jmp tape_load_success
 
 
+load_tape_normal_buf_MEMUSS:           // set MEMUSS (start address) as tape buffer 
+
+	lda TAPE1+1
+	sta MEMUSS+1
+	lda TAPE1+0
+	sta MEMUSS+0
+
+	rts
+
+
 #endif

c64/kernal/tape/tape_common.s

@@ -160,7 +160,7 @@ tape_handle_header:
 	sbc STAL+1
 	sta EAL+1
 	
-	// STAL = MEMUSS
+	// STAL = MEMUSS   XXX is it needed?
 
 	lda MEMUSS+0
 	sta STAL+0

c64/kernal/tape/tape_normal_get_data_1.s

@@ -3,7 +3,7 @@
 // #LAYOUT# *   *        #IGNORE
 
 //
-// Tape (normal) helper routine - data block reading
+// Tape (normal) helper routine - data block (primary) reading
 //
 // Stores data starting from MEMUSS, Carry set means error, on 0 bit .A is 0 too
 // .Y not equal to 0 - returns error if data block is longer (length includes checksum)
@@ -15,7 +15,7 @@
 #if CONFIG_TAPE_NORMAL
 
 
-tape_normal_get_data:
+tape_normal_get_data_1:
 
 	// Initialize checksum (RIPRTY, see http://sta.c64.org/cbm64mem.html)
 	// and pointers for error log and correction mechanism
@@ -26,7 +26,7 @@ tape_normal_get_data:
 
 	// FALLTROUGH
 
-tape_normal_get_data_block_1:
+tape_normal_get_data_1_block:
 
 	//
 	// Read the 1st copy of the block
@@ -35,19 +35,19 @@ tape_normal_get_data_block_1:
 	// Read sync of the block
 	ldy #$89
 	jsr tape_normal_sync
-	bcs tape_normal_get_data_fail
+	bcs tape_normal_get_data_1_fail
 	jsr tape_normal_get_marker
 
-tape_normal_get_data_loop_1:
+tape_normal_get_data_1_loop:
 
 	jsr tape_normal_get_byte
-	bcc tape_normal_get_data_loop_1_byte_OK
+	bcc tape_normal_get_data_1_loop_byte_OK
 	
 	// Problem reading a byte, try to add it to the error log
 
 	tsx
 	cpx #$20                           // just to be on a safe side
-	bcc tape_normal_get_data_fail      // branch if no more space in error log
+	bcc tape_normal_get_data_1_fail    // branch if no more space in error log
 
 	ldx PTR1
 	lda MEMUSS+0
@@ -60,18 +60,17 @@ tape_normal_get_data_loop_1:
 
 	// Addres added to error log, check if this was a checksum
 	jsr tape_normal_get_marker
-	bcc tape_normal_get_data_loop_1_advance
+	bcc tape_normal_get_data_1_loop_advance
-	bcs tape_normal_get_data_block_2
+	bcs tape_normal_get_data_1_success
 
-
+tape_normal_get_data_1_loop_byte_OK:
-tape_normal_get_data_loop_1_byte_OK:
 
 	jsr tape_normal_get_marker
 	bcc !+
 
 	// End of the block
 	jsr tape_normal_update_checksum
-	jmp tape_normal_get_data_block_2
+	jmp tape_normal_get_data_1_success
 
 !:
 	// Store byte, calculate checksum
@@ -82,7 +81,7 @@ tape_normal_get_data_loop_1_byte_OK:
 	
 	// FALLTROUGH
 
-tape_normal_get_data_loop_1_advance:
+tape_normal_get_data_1_loop_advance:
 
 	// Advance pointer
 #if !HAS_OPCODES_65CE02
@@ -91,48 +90,15 @@ tape_normal_get_data_loop_1_advance:
 	inw MEMUSS+0
 #endif
 
-	jmp tape_normal_get_data_loop_1
+	jmp tape_normal_get_data_1_loop
 
 
-tape_normal_get_data_block_2:
+tape_normal_get_data_1_success:
-
-	//
-	// Read the 2nd copy of the block
-	//
-
-	// First check if there is a need to read anything
-
-	// XXX
-
-	// Read sync of the block
-	ldy #$09
-	jsr tape_normal_sync
-	bcs tape_normal_get_data_fail
-	jsr tape_normal_get_marker
-
-	// XXX implement the second pass
-
-
-	lda PTR1
-	beq tape_normal_get_data_checksum
-
-	jmp tape_normal_get_data_fail
-
-
-
-
-tape_normal_get_data_checksum:
-
-	lda RIPRTY
-	cmp #$01                           // sets Carry if checksum verification fails
-
-	// FALLTROUGH
-
-tape_normal_get_data_done:
 
+	clc
 	rts
 
-tape_normal_get_data_fail:
+tape_normal_get_data_1_fail:
 
 	sec
 	rts

c64/kernal/tape/tape_normal_get_data_2.s

@@ -0,0 +1,51 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# *   KERNAL_0 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Tape (normal) helper routine - data block (backup) reading
+//
+
+
+#if CONFIG_TAPE_NORMAL
+
+
+tape_normal_get_data_2:
+
+	// First check if there is a need to read anything
+
+	lda PTR1
+	beq tape_normal_get_data_2_checksum
+
+	// Read sync of the block
+	
+	ldy #$09
+	jsr tape_normal_sync
+	bcs tape_normal_get_data_2_done    // Carry already set, will indicate error
+	jsr tape_normal_get_marker
+
+	// FALLTROUGH
+
+tape_normal_get_data_2_loop:
+
+	// XXX read missing bytes
+
+	sec
+	rts
+
+
+tape_normal_get_data_2_checksum:
+
+	// Validate checksum
+
+	lda RIPRTY
+	cmp #$01                           // sets Carry if checksum verification fails
+
+	// FALLTROUGH
+
+tape_normal_get_data_2_done:
+
+	rts
+
+
+#endif