Refactoring

1 files changed, 134 insertions, 0 deletions

diff --git a/loader.asm b/loader.asm
new file mode 100644
index 0000000..ca1c3bc
--- /dev/null
+++ b/loader.asm
@@ -0,0 +1,134 @@
+LOADER_REG_0 .rs 1
+LOADER_REG_1 .rs 1
+LOADER_REG_2 .rs 1
+LOADER_REG_3 .rs 1
+LOADER_REG_4 .rs 1
+LOADER_REG_5 .rs 1
+LOADER_REG_6 .rs 1
+LOADER_REG_7 .rs 1
+LOADER_CHR_START_H .rs 1
+LOADER_CHR_START_L .rs 1
+LOADER_CHR_START_S .rs 1
+LOADER_CHR_LEFT .rs 1
+LOADER_CHR_COUNT .rs 1
+LOADER_GAME_SAVE .rs 1
+LOADER_GAME_SAVE_BANK .rs 1
+LOADER_GAME_SAVE_SUPERBANK .rs 1
+
+loader:
+  ; loading game
+  jsr load_all_chr_banks ; load tiles
+	; setting all registers
+	lda LOADER_REG_0
+	sta $5000
+	lda LOADER_REG_1
+	sta $5001
+	lda LOADER_REG_2
+	sta $5002
+	lda LOADER_REG_3
+	sta $5003	
+	lda LOADER_REG_4
+	sta $5004
+	lda LOADER_REG_5
+	sta $5005
+	lda LOADER_REG_6
+	sta $5006
+	lda LOADER_REG_7
+	sta $5007
+  ; jumping to cleaner
+	jmp loader_clean_and_start
+
+load_all_chr_banks:
+	; loading tiles to CHR RAM for all banks
+	; how many 8KB parts left?
+	ldx <LOADER_CHR_LEFT
+	beq .done
+	dec <LOADER_CHR_LEFT
+	; high address byte
+	ldx <LOADER_CHR_START_H
+	stx $5000
+	; low address byte
+	lda <LOADER_CHR_START_L
+	sta $5001
+	; mask for 8KB banks
+	ldx #$FE
+	stx $5002
+	; target CHR bank
+	ldx <LOADER_CHR_COUNT
+	stx $5003
+	; source address
+	ldx #$00
+	stx <COPY_SOURCE_ADDR
+  ; source address overflow check
+	ldx <LOADER_CHR_START_S
+	bne .chr_not_null
+	ldx #$80
+	stx <LOADER_CHR_START_S
+.chr_not_null:
+	stx <COPY_SOURCE_ADDR+1
+  ; load 8KB of CHR
+	jsr load_chr
+  ; calculating next source address
+	lda <LOADER_CHR_START_S
+	clc
+	adc #$20
+	sta <LOADER_CHR_START_S
+  ; is it overflowed?
+	bcc .chr_s_not_inc
+  ; yes, increase source address for two banks
+	lda <LOADER_CHR_START_L	
+	clc
+	adc #2
+	sta <LOADER_CHR_START_L
+	lda <LOADER_CHR_START_H
+	adc #0
+	sta <LOADER_CHR_START_H	
+.chr_s_not_inc:
+  ; increase target CHR bank number
+	inc <LOADER_CHR_COUNT
+	jmp load_all_chr_banks
+.done:
+  rts
+
+	; loading tiles to CHR RAM
+load_chr:
+	lda #$00
+	sta $2006
+	sta $2006
+	ldy #$00
+	ldx #$20
+.loop:
+	lda [COPY_SOURCE_ADDR], y
+	sta $2007
+	iny
+	bne .loop
+	inc <COPY_SOURCE_ADDR+1
+	dex
+	bne .loop
+	rts
+
+  ; dirty trick :)
+loader_end:
+	.org $07E0
+loader_clean_and_start:
+	; clean memory
+	lda #$00
+	sta <COPY_SOURCE_ADDR
+	sta <COPY_SOURCE_ADDR+1
+	ldy #$02
+	ldx #$07
+.loop:
+	sta [COPY_SOURCE_ADDR], y
+	iny
+	bne .loop
+	inc <COPY_SOURCE_ADDR+1
+	dex
+	bne .loop
+.loop2:
+	sta [COPY_SOURCE_ADDR], y
+	iny
+	cpy #LOW(.loop2) ; to the very end
+	bne .loop2	
+	; Start game!
+	jmp [$FFFC]
+	.org loader_end