autogenerated scrolling code for head align tool

c64/kernal/tape/tape_head_align_gen_code.s

@@ -0,0 +1,132 @@
+// #LAYOUT# STD *        #TAKE
+// #LAYOUT# M65 KERNAL_1 #TAKE
+// #LAYOUT# *   *        #IGNORE
+
+//
+// Tape head alignemnt tool - helper code generator
+//
+
+
+#if CONFIG_TAPE_HEAD_ALIGN
+
+
+tape_head_align_gen_code:
+
+	// Setup generated code start address
+
+	lda #<__ha_scroll
+	sta SAL+0
+	lda #>__ha_scroll
+	sta SAL+1
+
+	// Setup initial source and destination addresses
+
+	ldy #<(__ha_chart + __ha_rows * (8 * 40) + 6)
+	sty __ha_lda_addr + 0
+	iny
+	sty __ha_sta_addr + 0
+
+	ldy #>(__ha_chart + __ha_rows * (8 * 40) + 6)
+	sty __ha_lda_addr + 1
+	sty __ha_sta_addr + 1
+
+	// Emit code to move 7 rows of one 8x8 cell
+!:
+	ldx #$07
+!:
+	jsr tape_head_align_gen_code_emit_pair
+
+	dec __ha_lda_addr + 0
+	dec __ha_sta_addr + 0
+
+	dex
+	bne !-
+
+	// Emit code to fetch a top row from the cell above
+
+    inc __ha_lda_addr + 0
+	sec
+	lda __ha_lda_addr + 0
+	sbc #<(8 * 40 - 7)
+	sta __ha_lda_addr + 0
+	lda __ha_lda_addr + 1
+	sbc #>(8 * 40 - 7)
+
+	sta __ha_lda_addr + 1
+
+	jsr tape_head_align_gen_code_emit_pair
+
+	// Prepare addresses for the next iteration
+
+	lda __ha_lda_addr + 0
+	sta __ha_sta_addr + 0
+	lda __ha_lda_addr + 1
+	sta __ha_sta_addr + 1
+
+	dec __ha_lda_addr + 0
+
+	// Now, new iteration - if needed
+
+	lda __ha_sta_addr + 0
+	cmp #<(__ha_chart + 7)
+	bne !--
+	lda __ha_sta_addr + 1
+	cmp #>(__ha_chart + 7)
+	bne !--
+
+	// Last pair to be generated starts from LDA #$00
+
+	lda #$A9
+	jsr tape_head_align_gen_code_emit_byte
+	lda #$00
+	jsr tape_head_align_gen_code_emit_byte
+
+	jsr tape_head_align_gen_code_emit_sta
+
+	// Emit RTS and quit
+
+	lda #$60
+	jmp tape_head_align_gen_code_emit_byte
+
+
+
+tape_head_align_gen_code_emit_pair:
+
+	lda #$BD                           // LDA absolute, x
+	jsr tape_head_align_gen_code_emit_byte
+
+	lda __ha_lda_addr + 0
+	jsr tape_head_align_gen_code_emit_byte
+	lda __ha_lda_addr + 1
+	jsr tape_head_align_gen_code_emit_byte
+
+	// FALLTROUGH
+
+tape_head_align_gen_code_emit_sta:
+
+	lda #$9D                           // STA absolute, x
+	jsr tape_head_align_gen_code_emit_byte
+
+	lda __ha_sta_addr + 0
+	jsr tape_head_align_gen_code_emit_byte
+	lda __ha_sta_addr + 1
+	
+	// FALLTROUGH
+
+tape_head_align_gen_code_emit_byte:
+
+	ldy #$00
+	sta (SAL), y
+#if HAS_OPCODES_65CE02
+	inw SAL
+#else
+	inc SAL+0
+	bne !+
+	inc SAL+1
+!:
+#endif
+
+	rts
+
+
+#endif // CONFIG_TAPE_HEAD_ALIGN