KONAMI VRC6 NES ROM TEMPLATE NESASM3

KONAMI VRC6 NESASM3 TEMPLATE

;THIS DOCUMENT IS VALID NESASM3 ASSEMBLY CODE AND SHOULD WORK AS LONG AS YOU FILL IN THE GAPS WITH YOUR OWN CODE!

	.inesprg 4    ; 1x 16KB PRG code
	.ineschr 2    ; 2x  8KB CHR data
	.inesmap 24	  ; Konami VRC6 Version 1 (Akumajou Densetsu)
	.inesmir 1    ; background mirroring (Vertical mirroring for Horizontal Scrolling)
	;nesasm3 doesn't seem to support save battery functionality. If you know how to do this please tell me.



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	;PUT YOUR MACROS, ZERO PAGE DEFINITIONS, AND RAM DEFINITIONS HERE!

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; HOW BANKING WORKS ON THE VRC6

; THE VRC6 HAS A 16K SWITCHABLE SECTION AND AN 8K SWITCHABLE SECTION. ALL PRG-ROM BANKS ON THE VRC6 ARE 8K.
; MAKE SURE YOU UNDERSTAND THIS, SINCE IT'S NOT WRITTEN DOWN ANYWHERE ON THE NESDEV WIKI!
; IF A BANK IS LOADED INTO THE 16K SECTION, IT IS LOADED INTO THE FIRST 8K OF THAT SECTION, AND THE BANK AFTER THAT IS LOADED INTO
; THE SECOND 8K OF THAT SECTION.

; BANK NUMBERS GO UP, WITH STARTING LOCATIONS OF $8000, $A000, $C000, AND BACK TO $8000 AGAIN.
; EACH BANK CAN BE LOADED IN A 16K OR 8K SECTION DURING RUNTIME BY WRITING THE DESIRED BANK NUMBER TO $8000 FOR THE 16K SECTION
; OR TO $C000 FOR THE 8K SECTION.

;EDIT: IT SEEMS THAT A BANK WITH .ORG $C000 IS THE ONLY TYPE OF BANK THAT CAN BE PROPERLY LOADED AT $C000. TESTING WITH BANKS THAT WEREN'T LISTED WITH .ORG $C000 SHOWED THAT THE BANKSWITCH WORKED BUT THE DATA COULDN'T BE READ PROPERLY.


;ANY NUMBER YOU SUPPLY TO THE VRC6 AS THE BANK NUMBER WHEN SWITCHING THE 16K SECTION GETS DOUBLED AUTOMATICALLY.
;THE 8K SECTION REGISTER, ON THE OTHER HAND, TAKES THE GIVEN VALUE AS-IS AND SWITCHES THE 8K SECTION TO THAT BANK.

; 16KB BANK EXAMPLE:
; LDA #$02
; STA $8000
; THE CARTRIDGE WILL LOAD BANK 4 AT $8000 AND BANK 5 AT $A000.

; 8KB BANK EXAMPLE:
; LDA #$02
; STA $C000
; THE CARTRIDGE WILL LOAD BANK 2 AT $C000.

; THE FIXED BANK IS ALWAYS AT $E000. YOUR RESET CODE MUST BE IN THE FIXED BANK OR THE PROGRAM WILL NOT WORK PROPERLY.
; NMI AND IRQ SHOULD ALSO BE IN THE FIXED BANK SINCE YOU CAN'T RELIABLY PREDICT WHEN THEY WILL EXECUTE.


; THE .inesprg NUMBER MUST BE EVEN OR THE EMULATOR WILL REFUSE TO RUN THE GAME.
; A VALID VRC6 CARTRIDGE MUST HAVE PRG-ROM DATA IN EXACT MULTIPLES OF 16K.
; YOU CAN ACHIEVE THIS BY ENSURING THAT THE NESASM BANK NUMBER OF THE FIXED BANK IS CONGRUENT TO 3 MOD 4.
; IF THAT'S TOO CONFUSING, CONSULT THE FOLLOWING CHART:

; .inesprg 2 = fixed bank is bank 3
; .inesprg 4 = fixed bank is bank 7
; etc.

;BANK SWITCHING


	.bank 0
	.org $8000
bank0start:
		;YOUR CODE OR DATA GOES HERE
bank0end:
	.ds 8192-(bank0end-bank0start)	;THIS IS USED TO CREATE THE CORRECT AMOUNT OF PADDING.

	.bank 1
	.org $A000
bank1start:
		;YOUR CODE OR DATA GOES HERE
bank1end:
	.ds 8192-(bank1end-bank1start)

	.bank 2
	.org $C000
bank2start:
		;YOUR CODE OR DATA GOES HERE
bank2end:
	.ds 8192-(bank2end-bank2start)

;if .inesprg = 2, stop here and bank 3 is set to .org $E000. otherwise continue.

	.bank 3
	.org $8000
bank3start:
		;YOUR CODE OR DATA GOES HERE
bank3end:
	.ds 8192-(bank3end-bank3start)
	.bank 4
	.org $A000
bank4start:
		;YOUR CODE OR DATA GOES HERE
bank4end:
	.ds 8192-(bank4end-bank4start)

	.bank 5
	.org $C000
bank5start:
		;YOUR CODE OR DATA GOES HERE
bank5end:
	.ds 8192-(bank5end-bank5start)

	.bank 6
	.org $8000
bank6start:
		;YOUR CODE OR DATA GOES HERE
bank6end:
	.ds 8192-(bank6end-bank6start)

	.bank 7	;this number will be different depending on how many switchable banks you have.
	.org $e000
reset:
		;your reset code goes here
		;the following VRC6-specific code will get you started with a "normal" PRG-ROM and CHR-ROM setup:
		;this will work even if you have the minimum .inesprg and .ineschr
	LDA #$00
	STA $8000 ;load bank 0 at $8000 and bank 1 at $A000

	LDA #$02
	STA $C000 ;load bank 2 at $C000

	LDA #$20
	STA $B003 ;"normal" mode as used by Castlevania 3

	LDX #$00
	STX $D000

	INX
	STX $D001

	INX
	STX $D002

	INX
	STX $D003

	INX
	STX $E000

	INX
	STX $E001

	INX
	STX $E002

	INX
	STX $E003
nmi:
		;your nmi code goes here
irq:
		;your irq code goes here

	.org $fffa
;these MUST be in the order below.
;their actual locations in the program don't matter as long as they are in the fixed bank.
	dw nmi
	dw reset
	dw irq
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; CHR-ROM BANKS

; These bank numbers pick up where the PRG-ROM bank numbers left off.
; These bank numbers are not actually used by the cartridge's banking system.
; Bank switching on CHR-ROM works differently, it depends on the value at memory-mapped register $B003 among other things.
; I won't go into too much detail here.

	.bank 8 ;this number will be different depending on how many switchable banks you have.
			;use the '.incbin' directive to insert your graphics data here.
	.bank 9 ;this number will be different depending on how many switchable banks you have.
			;use the '.incbin' directive to insert your graphics data here.