SNESDEV

Yesterday I returned to the PPU.c code. I knew that the VRAMLoad and CGRAMLoad needed to be reworked. The DMA transfer routine we were always getting data from bank $01. Since I start to having lots of ressource, I got stuck while implementing the score/status board. Here is the revised code :

void VRAMLoad(word far *src, word vramDst, word size) {
	// set address in VRam for read or write ($2116) 
	// + block size transfer ($2115)
	*(byte*)0x2115 = 0x80;
	*(word*)0x2116 = vramDst;

	
	// set DMA control register (1 word inc)
	// and destination ($21xx xx -> 0x18)
	*(word*)0x4300 = 0x1801;	

	// DMA channel x source address offset 
	// (low $4302 and high $4303 optimisation)
#asm
	lda %%src;					
	sta $4302;					
#endasm
	// DMA channel x source address bank
#asm
	lda %%src+2;				
	sta $4304;
#endasm

	// DMA channel x transfer size 
	// (low $4305 and high $4306 optimisation)
	*(word*)0x4305 = size;	

	// Turn on DMA transfer for this channel
	setINIDSPDirectValue(0x80);
	*(byte*)0x420b = 0x01;
	setINIDSPDirectValue(0x00);
}

I’m now using far pointer, here is a part of the ressource.h :

extern word far score_pic[];
extern word far score_pal[];
extern word far score_map[];

So now I can copy from anywhere in ROM to VRAM or CGRAM  without any problem.

++ Lint

This entry was posted on Tuesday, July 8th, 2008 at 10:19 am and is filed under Snes, Software dev. You can follow any responses to this entry through the RSS 2.0 feed. Responses are currently closed, but you can trackback from your own site.