diff options
| author | Alexey 'Cluster' Avdyukhin <clusterrr@clusterrr.com> | 2020-09-27 15:39:57 +0300 |
|---|---|---|
| committer | Alexey 'Cluster' Avdyukhin <clusterrr@clusterrr.com> | 2020-09-27 15:39:57 +0300 |
| commit | 16b86f0194c4dd4e0a83a741d319c89850e35898 (patch) | |
| tree | 7a7293fe6e0d45532dca6122835e099c3ea52e12 /banking.asm | |
| parent | e02b7596d64dd9692567dfaccc7eeea1fbdfa958 (diff) | |
Banking, 512KB of CHR RAM support
Diffstat (limited to 'banking.asm')
| -rw-r--r-- | banking.asm | 30 |
1 files changed, 19 insertions, 11 deletions
diff --git a/banking.asm b/banking.asm index 590d08c..eb9b7b0 100644 --- a/banking.asm +++ b/banking.asm @@ -1,3 +1,4 @@ +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 @@ -7,11 +8,13 @@ PRG_RAM_BANKS .equ 4 ; number of PRG RAM banks 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 - sta $5003 - sta $5005 + jsr sync_banks + ; mirroring lda #%00001000 ; store config sta <CART_CONFIG @@ -20,24 +23,28 @@ banking_init: ; select 16KB PRG bank at $8000-$BFFF (from A) select_prg_bank: - sta PRG_BANK + sta <PRG_BANK jsr sync_banks rts ; select 8KB CHR bank (from A) select_chr_bank: - sta CHR_BANK + sta <CHR_BANK jsr sync_banks rts ; select 8KB FRAM bank (from A) select_prg_ram_bank: - sta PRG_RAM_BANK + sta <PRG_RAM_BANK jsr sync_banks rts ; actual bank selection sync_banks: + lda <PRG_SUPERBANK + sta $5001 + lda <PRG_SUPERBANK+1 + sta $5000 lda CHR_BANK pha and #%00011111 @@ -45,16 +52,17 @@ sync_banks: pla asl A asl A - sta TMP - lda PRG_BANK + and #%10000000 + sta <TMP + lda <PRG_BANK asl A asl A and #%01111100 - ora TMP - sta TMP - lda PRG_RAM_BANK + ora <TMP + sta <TMP + lda <PRG_RAM_BANK and #%00000011 - ora TMP + ora <TMP sta $5005 rts |