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PRG_SUPERBANK .rs 2 ; PRG superbank
PRG_BANK .rs 1 ; PRG_A BANK
CHR_BANK .rs 1 ; CHR_A BANK
PRG_RAM_BANK .rs 1 ; PRG RAM BANK
CART_CONFIG .rs 1 ; variable to store last config
PRG_RAM_BANKS .equ 4 ; number of PRG RAM banks
BANKS_TMP .rs 1
banking_init:
; set mirrong, disabe CHR writing, PRG-RAM and flash writing
lda #0
sta <PRG_SUPERBANK
sta <PRG_SUPERBANK+1
sta <PRG_BANK
sta <CHR_BANK
sta <PRG_RAM_BANK
jsr sync_banks
; mirroring
lda #%00001000
; store config
sta <CART_CONFIG
sta $5007
rts
; select 16KB PRG bank at $8000-$BFFF (from A)
select_prg_bank:
sta <PRG_BANK
jsr sync_banks
rts
; select 8KB CHR bank (from A)
select_chr_bank:
sta <CHR_BANK
jsr sync_banks
rts
; select 8KB FRAM bank (from A)
select_prg_ram_bank:
sta <PRG_RAM_BANK
jsr sync_banks
rts
; actual bank selection
sync_banks:
pha
lda <PRG_SUPERBANK
sta $5001
lda <PRG_SUPERBANK+1
sta $5000
lda CHR_BANK
pha
and #%00011111
sta $5003
pla
asl A
asl A
and #%10000000
sta <BANKS_TMP
lda <PRG_BANK
asl A
asl A
and #%01111100
ora <BANKS_TMP
sta <BANKS_TMP
lda <PRG_RAM_BANK
and #%00000011
ora <BANKS_TMP
sta $5005
; for UNROM compatibility
txa
pha
lda <PRG_BANK
tax
sta unrom_bank_data, x
pla
tax
pla
rts
enable_prg_ram:
lda <CART_CONFIG
ora #%00000001
sta <CART_CONFIG
sta $5007
rts
disable_prg_ram:
lda <CART_CONFIG
and #%11111110
sta <CART_CONFIG
sta $5007
rts
enable_chr_write:
lda <CART_CONFIG
ora #%00000010
sta <CART_CONFIG
sta $5007
rts
disable_chr_write:
lda <CART_CONFIG
and #%11111101
sta <CART_CONFIG
sta $5007
rts
enable_flash_write:
lda <CART_CONFIG
ora #%00000100
sta <CART_CONFIG
sta $5007
rts
disable_flash_write:
lda <CART_CONFIG
and #%11111011
sta <CART_CONFIG
sta $5007
rts
enable_four_screen:
lda <CART_CONFIG
ora #%00100000
sta <CART_CONFIG
sta $5007
rts
disable_four_screen:
lda <CART_CONFIG
and #%11011111
sta <CART_CONFIG
sta $5007
rts
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