Banking

1 files changed, 105 insertions, 3 deletions

diff --git a/banking.asm b/banking.asm
index 76d99bd..4bfa054 100644
--- a/banking.asm
+++ b/banking.asm
@@ -1,7 +1,109 @@
-select_bank:
-  tax
-  sta unrom_bank_data, x
+ 
+PRG_BANK .rs 1 ; PRG_A BANK
+CHR_BANK .rs 1 ; CHR_A BANK
+FRAM_BANK .rs 1 ; FRAM BANK
+CART_CONFIG .rs 1 ; variable to store last config
+
+banking_init:
+  ; set mirrong, disabe CHR writing, PRG-RAM and flash writing
+  lda #0
+  sta <PRG_BANK
+  sta <CHR_BANK
+  sta <FRAM_BANK
+  sta $5003
+  sta $5005
+  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
+
+  ; actual bank selection
+sync_banks:
+  lda CHR_BANK
+  pha
+  and #%00011111
+  sta $5003
+  pla
   asl A
   asl A
+  sta TMP
+  lda PRG_BANK
+  asl A
+  asl A
+  and #%01111100
+  ora TMP
+  sta TMP
+  lda FRAM_BANK  
+  and #%00000011
+  ora TMP
   sta $5005
   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