RESOURCE: SNES assembly code tutorial

[smozoma]

Pretty impressive tutorial from a Super Mario World editing forum:

http://www.smwcentral.net/?p=thread&id=16714

Here is the table of contents:

-------------------------

1. BASIC WORKSHOP

1.1 - HEX AND BINARY

1.2 - A X Y REGISTERS

1.3 - LDA, STA, RTS, INC, DEC, INX, INY, STZ, ADC, SBC.

1.4 - DIRECT PAGE, TCD, TDC, XBA.

1.5 - BANKS

1.6 - EMULATION MODE, PROCESSOR FLAGS, REP, SEP, CLC, SEC, CLV, SED, SEI, CLI, CLD, CONDITIONAL OPERATIONS.

1.7 - JUMPS.

1.8 - INDEXING

1.9 - STACK, STACK POINTER, TSC, TCS, TXS, TSX.

1.10 - TRANSFERRING

--------------------------

2. SEMI-ADVANCED WORKSHOP

2.1 - VECTORS, H/V-BLANKING, INTERRUPTS

2.2 - BITWISE OPERATIONS

2.3 - VARIOUS PPU REGS

2.4 - DMA AND HDMA

2.5 - BLOCK MOVES -> MVN, MVP

2.6 - MORE ADDRESSING MODES

2.7 - USELESS OPCODES

--------------------------

I found it when I was trying to figure out the difference between DMA mode 0 and mode 1.

mode 0 is 4 layers + 4 colours per palette

mode 1 is 3 layers + 16 colours per palette.

mode 1 would be used when loading a player portrait, since they're 16 colours.

i suspect mode 0 is used to show team banners (upper half of banner = 4 colours, lower half = 4, text = 4..), but that's a guess. EDIT: reading the document made me realize that banner idea is wrong.. the mode 0 stuff i was seeing was actually changing palettes..

Edited April 5, 2010 by smozoma

[chaos]

Here are some other references on:

SNES Graphics: http://web.archive.org/web/20071111200111/...u/qsnesdoc.html

General SNES programming info: http://en.wikibooks.org/wiki/Super_NES_Programming

Some of this info. is really good and might be helpful as well.

[smozoma]

Apparently Anomie's documents are good:

http://www.romhacking.net/?category=&P...itle=&desc=

Register Map:

http://www.romhacking.net/docs/%5B196%5Dregs.txt (Anomie's)

http://fh.digitalmenagerie.org/coding/Snesmap.txt (someone else's)

Found this stuff when looking for info about register 4202:

4202  wb++++ WRMPYA - Multiplicand A
4203  wb++++ WRMPYB - Multiplicand B
	mmmmmmmm

	Write $4202, then $4203. 8 "machine cycles" (probably 48 master cycles)
	after $4203 is set, the product may be read from $4216/7. $4202 will
	not be altered by this process, thus a new value may be written to
	$4203 to perform another multiplication without resetting $4202.

	The multiplication is unsigned.

That bit about cycles is important: after setting 4202 and 4203 (to say 2 and 3), you need to wait a while (run some other instructions) before the result is ready. Once the result is ready, you can actually set a new value into 4202 (say 10), then immediately pull the old result from 4216 (2x3=6) before it changes to the new result a few cycles later (10x33=30).

Edited April 7, 2010 by smozoma