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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_GAME_SAVE .rs 1
LOADER_GAME_SAVE_BANK .rs 1
LOADER_GAME_SAVE_SUPERBANK .rs 1
loader:
; loading game
; 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
; 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
load_all_chr_banks:
; loading tiles to CHR RAM for all banks
; how many 8KB parts left?
lda #0
sta <CHR_BANK
sta <PRG_BANK
sta <COPY_SOURCE_ADDR
lda <LOADER_CHR_START_L
sta <PRG_SUPERBANK
lda <LOADER_CHR_START_H
sta <PRG_SUPERBANK+1
.loop
lda <LOADER_CHR_LEFT
beq .done
dec <LOADER_CHR_LEFT
jsr sync_banks
; source address
lda <LOADER_CHR_START_S
sta <COPY_SOURCE_ADDR+1
; load 8KB of CHR
jsr load_chr
; calculating next source address
lda <LOADER_CHR_START_S
clc
adc #$20
sta <LOADER_CHR_START_S
cmp #$C0
; is it overflowed?
bne .chr_s_not_inc
; yes
lda #$80
sta <LOADER_CHR_START_S
lda <PRG_SUPERBANK
clc
adc #1
sta <PRG_SUPERBANK
lda <PRG_SUPERBANK+1
adc #0
sta <PRG_SUPERBANK+1
.chr_s_not_inc:
; increase target CHR bank number
inc <CHR_BANK
jmp .loop
.done:
jsr banking_init
rts
; loading tiles to CHR RAM
load_chr:
jsr enable_chr_write
lda #$00
sta PPUADDR
sta PPUADDR
ldy #$00
ldx #$20
.loop:
lda [COPY_SOURCE_ADDR], y
sta PPUDATA
iny
bne .loop
inc <COPY_SOURCE_ADDR+1
dex
bne .loop
jsr disable_chr_write
rts
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