some SNES programming questions
From: vic@physci.psu.edu (Vic Ricker)
To: "Super Famicom Development Group" <famidev@busop.cit.wayne.edu>
Subject: Re: some programming questions
Date: Tue, 9 Nov 93 20:20:35 EST
Hi Folks.
I need help with a few SNES programming questions...
(1) Can anyone tell me how to make noises come out of my SNES?
Insert your favorite cart, power up the TV, switch the snes power to ON.. :-)
(3) Is the sprite position table held in RAM or VRAM? And how do the 5 address bits in $2101 relate to this location?
The sprite images are stored in VRAM. The palettes for the sprites are stored in CGRAM. The coordinates and char attributes are stored in OAM.
The format of each OBJ is:
OBJ H position: 8 bits
OBJ V position: 8 bits
V flip: 1 bit
H flip: 1 bit
OBJ priority: 2 bits
color palette: 3 bits
character name: 9 bits
there are 128 of these in sequence making 512 bytes then 32 bytes
follow in the format:
size: 1 bit
x msb: 1 bit
there are 128 of these (one for every OBJ) making 32 more bytes.
$2101 is OBJSEL
it chooses the size of sprites to use and also sets the address of the images in VRAM. the top 3 bits chose the size:
000 means 8x8 and 16x16 sprites
001 8x8 and 32x32
010 8x8 and 64x64
011 16x16 and 32x32
100 16x16 and 64x64
101 32x32 and 64x64
the other bits are the address in vram of the sprite images.
$2102-$2103 is OAMADDL/H
the lower 9 bits are the address for accessing the OAM. (like $2116 for VRAM) the high bit (15) enables priority rotation (causes OBJ's to change priority as to keep them from disappearing totally when time out and range over occur.)
$2104 is OAMDATA
it is the write register for the OAM. (like $2118-$2119 for VRAM)
$2138 is *OAMDATA
it is the read register for the OAM.
Hope this gives you enough to play with. Most is from memory, I hope its all correct. :-)
Lemme know if you have questions.
