SnesLab - User contributions [en]

Bithacks

2021-04-06T08:11:47Z

Randomdude999: fix macro arg syntax

Bithacks are optimization tricks that utilize information in bits and [https://en.wikipedia.org/wiki/Bit_manipulation bit manipulation]
to accomplish their tasks. Usually they work in a slightly non-obvious way, (the most famous being the [https://en.wikipedia.org/wiki/Fast_inverse_square_root fast inverse sqrt]), and bit manipulation in general is harder on the 65c816. To that end here is a collection of some useful tricks.
 
'''Note: cycle counts are intended to be a worst case measure.'''

== Math Bithacks ==
'''Signed Division By 2''' ''(5 bytes / 10 cycles)''
 
inputs: A
 
outputs: A
<pre>
STA $00
ASL $00
ROR
</pre>

'''Signed Division By 2n''' ''(6+2n bytes / 5+2n cycles)''
 
inputs: A, n
 
outputs: A
<pre>
; signed division by two, n times
macro SignedDiv_2N(n)
BMI ?negative
LSR #<n>
BRA ?end
?negative:
LSR #<n>
ORA #($FF<<(8-<n>)) ; sign extension
?end:
endmacro
</pre>

== Misc. Tricks ==
As this list grows tricks here will be consolidated into their own sections. Clever optimization tricks that aren't necessarily what someone might personally call a "bithack" are okay here as well!

Useful Code Snippets

2019-08-09T02:01:47Z

Randomdude999: make the long branch macros use macro-local labels

Useful code snippets for the 65c816 ASM and general SNES hardware.

== 65c816 S-CPU ==

=== General ===

==== Wait for H-Blank ====

<pre>
-
BIT $4212
BVS -
-
BIT $4212
BVC -
</pre>

==== Inverse the accumulator (8-bit) ====

<pre>
EOR #$FF
INC
</pre>

==== Inverse the accumulator (16-bit) ====

<pre>
EOR #$FFFF
INC
</pre>

==== Toggle Carry Flag Macro ====

<pre>
macro XOC()
BCC ?set
CLC
BRA ?done
?set: SEC
?done:
endmacro
</pre>

==== Long Branch Macros ====
Useful if your want to branch more than 0x80 bytes forward/backwards.

<pre>
macro JEQ(branch)
BNE ?branch
JMP <branch>
?branch:
endmacro

macro JNE(branch)
BEQ ?branch
JMP <branch>
?branch:
endmacro

macro JCC(branch)
BCS ?branch
JMP <branch>
?branch:
endmacro

macro JCS(branch)
BCC ?branch
JMP <branch>
?branch:
endmacro

macro JPL(branch)
BMI ?branch
JMP <branch>
?branch:
endmacro

macro JMI(branch)
BPL ?branch
JMP <branch>
?branch:
endmacro

macro JVC(branch)
BVS ?branch
JMP <branch>
?branch:
endmacro

macro JVS(branch)
BVC ?branch
JMP <branch>
?branch:
endmacro
</pre>

=== SMW Hacking ===

==== Custom block template ====
by [[User:Alcaro|Alcaro]]
Works with SA-1.

<pre>
db $42 ; or db $37
JMP MarioBelow : JMP MarioAbove : JMP MarioSide
JMP SpriteV : JMP SpriteH : JMP MarioCape : JMP MarioFireball
JMP TopCorner : JMP BodyInside : JMP HeadInside
; JMP WallFeet : JMP WallBody ; if using db $37

MarioBelow:
MarioAbove:
MarioSide:

TopCorner:
BodyInside:
HeadInside:

WallFeet:
WallBody:

SpriteV:
SpriteH:

MarioCape:
MarioFireball:
RTL
</pre>

==== Decompress GFX File ====
by [[User:Vitor Vilela|Vitor Vilela]]
Works with SA-1.

<pre>
; Decompress input GFX file
; Must be called from SNES CPU.
; SA-1 is automatically invoked on SA-1 Pack ROMs.

STZ $00
REP #$20
LDA #$7EAD ; destination buffer = $7EAD00
STA $01
LDA #$0080 ; deoompress ExGFX80.bin ..
JSL $0FF900
</pre>

==== Get acts like from map16 number ====
by [[User:Vitor Vilela|Vitor Vilela]]
Works with SA-1.

<pre>
; $00 = map16 tile
get_act_like:
LDA $06F624
STA $02
LDA $06F625
STA $03
LDA $06F626
STA $04

REP #$30
LDA $00
AND #$3FFF
ASL
TAY
LDA [$02],y
STA $00
SEP #$30
RTS
</pre>

==== Find free OAM slot ====
by [[User:Vitor Vilela|Vitor Vilela]]
SA-1 hybrid.

<pre>
; Routine for finding a free OAM slot
; NMSTL compatible. Tested against Level ASM, Overworld ASM.

find_oam:
LDY #$FC
- LDA $02FD|!addr,y
CMP #$F0
BNE +
CPY #$3C
BEQ +
DEY
DEY
DEY
DEY
BRA -
+ RTS
</pre>

==== Erase current save file ====
by [[User:Sixtare|Sixtare]]

<pre>
Erase:
REP #$10
LDA $010A
CMP #$01
BEQ .01
BCS .02
.00
LDX #$008F
JMP .delete

.01
LDX #$011E
JMP .delete

.02
LDX #$01AD
.delete
LDY #$008F
LDA #$00
- STA $700000,x
STA $7001AD,x
DEX
DEY
BPL -
SEP #$10
RTS
</pre>

== 65c816 SA-1 CPU ==
Some snippets present on [[#65c816_S-CPU|S-CPU]] section works with SA-1 CPU as well.

=== General ===

==== Unsigned 16 bit x 16 bit = 32 bit multiplication ====
by [[User:Akaginite|Akaginite]]

<pre>
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; 16bit * 16bit Multiplication SA-1 version
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;
; Parameters
; $00-$01 : Multiplicand
; $02-$03 : Multiplier
; Return values
; $04-$07 : Product
;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;;

MathMul16_16: STZ $2250
REP #$20
LDA $00
STA $2251
ASL A
LDA $02
STA $2253
BCS +
LDA.w #$0000
+ BIT $02
BPL +
CLC
ADC $00
+ CLC
ADC $2308
STA $06
LDA $2306
STA $04
SEP #$20
RTS
</pre>

SNES ROM Header

2019-08-07T10:06:35Z

Randomdude999: Checksum calculation info

All [[SNES]] gamepaks have an internal header that is used to identifying the game, producer, region and technical aspects of the ROM. It's often referred as '''Internal ROM Header''' or '''SNES Software Specification'''.

Although it's not required to run a game on real hardware, the SNES ROM Header was used during the Nintendo approval process for validation and it's also used by the SNES emulators to identify and determine the memory layout and ROM type.

The data starts at SNES address $00:FFB0 and ends at $00:FFDF. $00:FFE0 though $00:FFFF contains the SNES vector information and '''it's actually used''' by the SNES CPU to determine where to execute when an interrupt occurs.

== ROM Registration Data ==

{| class="wikitable"
|-
! Address !! Length !! Data Name Type
|-
| $00:FFB0 || 2 bytes || Maker Code
|-
| $00:FFB2 || 4 bytes || Game Code
|-
| $00:FFB6 || 7 bytes || Fixed Value
|-
| $00:FFBD || 1 byte || Expansion RAM Size
|-
| $00:FFBE || 1 byte || Special Version
|-
| $00:FFBF || 1 byte || Cartridge Type (Sub-number)
|-
| $00:FFC0 || 21 bytes || Game Title Registration
|-
| $00:FFD5 || 1 byte || Map Mode
|-
| $00:FFD6 || 1 byte || Cartridge Type
|-
| $00:FFD7 || 1 byte || ROM Size
|-
| $00:FFD8 || 1 byte || RAM Size
|-
| $00:FFD9 || 1 byte || Destination Code
|-
| $00:FFDA || 1 byte || Fixed Value
|-
| $00:FFDB || 1 byte || Mask ROM Version
|-
| $00:FFDC || 2 bytes || Complement Check
|-
| $00:FFDE || 2 bytes || Check Sum
|}

== Data Name Types ==

=== Maker Code ===
=== Game Code ===
=== Fixed Value ===
=== Expansion RAM Size ===
=== Special Version ===
=== Game Title Specification ===
=== Cartridge Configuration ===
==== Map Mode ====
==== Cartridge Type ====
===== Sub-Number =====
==== ROM Size ====
==== RAM Size ====

=== Destination Code ===
=== Mask ROM Version ===
=== ROM Verification ===
==== Complement Check ====
This is the 16-bit complement (bit-inverse) of the checksum. This is used so that the checksum value cancels itself out when calculating the real checksum.
==== Check Sum ====
This is simply the 16-bit sum of all bytes in the ROM. For power-of-2-sized ROMs, no mirroring is used, each byte of ROM is counted exactly once.

For non-power-of-2-sized ROMs (e.g. 2.5MB or 6MB), first the checksum for the largest power-of-2 area smaller than the ROM size (so 4MB for 6MB ROMs, 2MB for 2.5MB ROMs) is computed normally. Then the remaining part is repeated until it's the same size as the first part (so the last 2MB of a 6MB ROM is repeated once so both halves are 4MB, and the last 512KB of a 2.5MB ROM is repeated 4 times so both halves are 2MB). Then its checksum is computed and the checksums of the 2 halves are added to get the final checksum.

List of SNES ROM hacking tools

2019-07-12T10:55:48Z

Randomdude999: add a few more general tools

== General ==
=== ASM patchers ===
* [https://github.com/RPGHacker/asar Asar]
* [https://byuu.org/tool/bass bass]
* [https://www.smwcentral.net/?p=section&a=details&id=4615 xkas] (old and slightly buggy, but used to be very popular)

=== Binary patchers ===
* [https://github.com/Alcaro/Flips FLIPS] (.bps, .ips)
* [http://fusoya.eludevisibility.org/lips/index.html Lunar IPS] (.ips)

=== Emulators ===
* [https://byuu.org/emulation/bsnes/ bsnes]
* [https://github.com/snes9xgit/snes9x Snes9x]
* [http://zsnes.com/ ZSNES] (inaccurate, but fast and used to be very popular)

=== Emulators/Debuggers ===
* [https://github.com/devinacker/bsnes-plus bsnes-plus]
* [https://github.com/SourMesen/Mesen-S Mesen-S] (WIP, doesn't emulate enhancement chips yet)

== SMW Hacking ==
=== Editors ===
* [https://fusoya.eludevisibility.org/lm/index.html Lunar Magic]

=== Inserters ===
* [https://github.com/VitorVilela7/UberASMTool UberASM Tool]
* [https://github.com/JackTheSpades/SpriteToolSuperDelux PIXI]
* [https://smwc.me/1491239 GIEPY]
* [https://www.smwcentral.net/?p=section&a=details&id=17546 AddmusicK]

=== Converters ===
* [https://github.com/VitorVilela7/SPCtoMML SPCtoMML]
* [https://github.com/VitorVilela7/SnesGFX SnesGFX]

== YI Hacking ==
=== Editors ===
* [https://www.smwcentral.net/?p=section&a=details&id=4645 Golden Egg]

=== Inserters ===
* [https://dl.dropbox.com/s/oqsnu42mg76runs/AddMusicY%20Beta.zip AddmusicY]

Template:Subpages

2019-05-24T14:37:38Z

Randomdude999: Lists all subpages of the current page, or optionally any specified page.

{{Special:PrefixIndex|prefix={{PAGENAME:{{{1|{{FULLPAGENAME}}}}}}}/|namespace={{NAMESPACENUMBER:{{{1|{{FULLPAGENAME}}}}}}}|stripprefix=1}}<noinclude>
Lists all subpages of the current page, or optionally any specified page.

To list subpages of the current page, use <code><nowiki>{{Subpages}}</nowiki></code>. To list subpages of a specific page, use <code><nowiki>{{Subpages|pagename}}</nowiki></code>. <code>pagename</code> may be in any namespace.

User:Randomdude999

2019-05-14T13:31:10Z

Randomdude999: Initial commit

{{DISPLAYTITLE:User: randomdude999}}
From Estonia.

I like programming sometimes. Competent in Python, C, C++, HTML/CSS, JS, Lua, 65c816 assembly (+SNES register set), PHP, Bash, and (a long time ago) wiki markup and Java.

[https://github.com/randomdude999 GitHub profile], [https://www.smwcentral.net/?p=profile&id=32552 SMWC profile]