65816 Assembly programming for the SNES and Super Famicom

The Super Nintendo (AKA Super Famicom)  was the successor to the NES... relatively late to the 16 bit game, the SNES made the unusual choice to not use the 68000 CPU for its processor, favoring the slower and less efficient 65186... this is rumored to be because during development backwards compatibility with the NES was planned... The 65186 is a true 16 bit CPU, but it has a 6502 compatibility mode, in which it works exactly like a 6502, and we can perform basic SNES programming without even using a 16 bit command!

Cpu 3.58 mhz 65816  Ram 128k Vram 64k Tiles 1024 x 4 or 16 color Sprites 128 onscreen (32 per line) Resolution 512x448 Colors 256 (16 per tile) from 32768  Sound chip 64k DSP 8 channel  SPC700 The UK SNES PSU outputs 9V AC the Japanese Super Famicom PSU outputs 10V DC - CENTER NEGATIVE BE CAREFUL! adapters that output AC are very rare and will kill most systems - and Center negative was common for 80's Japanese systems, but is very rare these days - YOU HAVE BEEN WARNED!

ChibiAkumas Tutorials

Useful Document
SNES Documentation v2.30: Written by Yoshi
nocash SNES hardware specifications

Memory Map

Lets look at this example of a 16x16 sprite in AkuSprite Editor... Akusprite editor is designed for 8x8 sprites, but we can export a 16x16 one in the following way If we want to export this quickly, so we can use it as a single doublesize sprite, one option is to tick the 'FixedSize' tickbox, and set the size to 128,16 This will export the sprite correctly - of course there will be a lot of unused space in the exported file... so we would want to combine all our 16x16 together into a single image Generally it would be easier to build up a 16x16 sprite from 4 8x8 sprites

Sprite Sizes

Sprite size is set for all sprites, but each sprite can either be normal or large defined by a single bit from address $0100 onwards

Sprite Definitions - OAM Data

The SNES has 128 hardware sprites.

Selecting a HL address is done by setting registers $2102 (L) and $2103 (H)

SNES Joypad

Presumably because of the planned backwards compatibility, the SNES actually uses the same ports in the same way as the NES! However, because the SNES has more buttons, we can do 16 reads rather than 8 to get the extra buttons.

The SNES firmware also reads in these ports automatically, and stores these in ram - we can use these versions if we prefer.

Ports

WD=Write Double byte
2=Write 2 byte word

Sound on the SNES via the SPC700
To make sound on the SNES we have to use it:s SPC700 processor! what's the SPC700? well it's an 8 bit dedicated sound CPU with 64k of isolated memory - meaning that it can't be directly accessed from the main CPU!
The SPC700 is a great sound processor, used by the Super Nintendo and many other systems like... er.. the super nintendo!
Ok, so nothing else uses it, and it's a total pain!  while it's sound ability is good, its a real hassle to program... it uses it's own special instruction set, and its bytecode matches no other CPU, and data has to be transferred to it using a special procedure because we can't access it's memory directly.

The CPU is 8 bit and Little endian, so $1234 is stored in ram as $34,$12... it's registers are the same as the 6502, but it has some 16 bit commands that use YA as a 16-bit pair like the Z80

 it has a ZeroPage, but the ZeroPage is referred to as the DirectPage, as it can be at $00xx or $01xx... $01xx is also used as the Stack

Most data transfer commands are done with MOVe commands (like the 68000), but like the z80, the destination is on the left... for example:
mov a, #$00     ;Set A to $00

I'm not planning to go into greater detail than I need on this CPU, so please see the tutorials below:
Best SP700 reference
Also a good tutorial

The SPC700 Memory Map

The SPC700 Registers

SPC700 and VASM