Syntax

The examples on this page are interactive: edit the source and click Assemble to build it in your browser (powered by the WebAssembly build of nessemble). Assembled bytes are shown as a hex dump and can be downloaded.

Numbers

Binary, decimal, octal, hexadecimal, and ASCII character are all valid numbers.

Symbols

Mathematical Operators

Comparison Operators

Special

Labels

Named

Named label declarations must be in the follow format:

NAME:

• NAME - Label name, required.

Example:

    LDX #$08
loop:
    DEX
    BNE loop
    BRK

Output:

00000000  a2 08 ca d0 fd 00                                 |......|
00000006

Try it:

A label that names a subroutine can carry its calling convention — the registers it takes, returns, and destroys — in comments the tooling reads. See Documenting routines.

Temporary

Temporary/un-named labels may also be declared by placing only a colon.

:

To jump to a temporary label, the direction and count of the jumps must be given.

JMP :[+-]

[+-] - Direction, required.

N-number of +s means to jump to the temporary label that is N temporary labels further down in the code.

N-number of -s means to jump to the temporary label that is N temporary labels further up in the code.

Example:

    LDX #$08
:
    DEX
    BNE :-
    BRK

Output:

00000000  a2 08 ca d0 fd 00                                 |......|
00000006

Try it:

Mnemonics

All 56 mnemonics are supported:

Read more about 6502 opcodes here.

In addition, 24 illegal/undocumented mnemonics may be used when assembled with the -u, --undocumented flag.

Read more about undocumented 6502 opcodes here.

Addressing Modes

nessemble uses square brackets [] instead of parentheses () in its addressing modes because the latter are used to indicate precedence in mathematical operations.

Read more about 6502 addressing modes here.

Functions

Pseudo-Instructions

.ascii

Convert ASCII string to bytes.

Usage:

.ascii "STRING"[(+/-)NUMBER]

• "STRING" - String, required. ASCII string to turn into bytes. Must be within quotes.
• (+/-)NUMBER - Number, optional. Amount to increase/decrease ASCII values.

Example:

.ascii "When, in disgrace with fortune and men's eyes"

Output:

00000000  57 68 65 6e 2c 20 69 6e  20 64 69 73 67 72 61 63  |When, in disgrac|
00000010  65 20 77 69 74 68 20 66  6f 72 74 75 6e 65 20 61  |e with fortune a|
00000020  6e 64 20 6d 65 6e 27 73  20 65 79 65 73           |nd men's eyes|
0000002d

Try it:

The +/- operators may also be used to increase/decrease the output.

Example:

.ascii "I all alone beweep my outcast state"-32

Output:

00000000  29 00 41 4c 4c 00 41 4c  4f 4e 45 00 42 45 57 45  |).ALL.ALONE.BEWE|
00000010  45 50 00 4d 59 00 4f 55  54 43 41 53 54 00 53 54  |EP.MY.OUTCAST.ST|
00000020  41 54 45                                          |ATE|
00000023

.checksum

Calculate crc32 checksum.

Usage:

.checksum LABEL

• LABEL - Label, required. Label at which to start generating the checksum.

Example:

start:
    LDA #$01
    STA <$02
    .checksum start

Output:

00000000  a9 01 85 02 b8 1f ee 86                           |........|
00000008

The checksum is b8 1f ee 86.

Checksums may only be performed on preceding data.

Try it:

.chr

Set CHR bank index.

Usage:

.chr NUMBER

• NUMBER - Number, required. CHR bank index.

Example:

.chr 0

CHR banks are 2K bytes (0x2000) in size.

.color

Convert hex color to NES color.

Finds the closest valid NES color to the given hex color.

Usage:

.color NUMBER[, NUMBER, ...]

• NUMBER - Number, required. At least one number is required.
• , NUMBER, ... - Number(s), optional. Additional comma-separated numbers may be used.

Example:

.color $FF0000

Output:

00000000  16                                                |.|
00000001

Read more about the NES color palette here.

In an editor connected to the language server, hovering .color previews the palette entries the whole argument list maps to, and hovering a single argument previews just that color.

Try it:

.db

Define 8-bit byte(s).

Usage:

.db NUMBER[, NUMBER, ...]

• NUMBER - Number, required. At least one number is required.
• , NUMBER, ... - Number(s), optional. Additional comma-separated numbers may be used.

Example:

.db $12, $34

Output:

00000000  12 34                                             |.4|
00000002

Try it:

A trailing comma continues the list onto the next line, so a long run of bytes can be wrapped across several indented lines:

.db $00, $01, $02, $03,
    $04, $05, $06, $07

The same line-continuation rule applies to every comma-separated data directive (.dw, .fill, .color, .hibytes, .lobytes, and .defchr).

.defchr

Define CHR tile.

Only numbers from 0-3 may be used: 0 representing black, 1 dark grey, 2 light grey, and 3 representing white.

Usage:

.defchr XXXXXXXX,
        XXXXXXXX,
        XXXXXXXX,
        XXXXXXXX,
        XXXXXXXX,
        XXXXXXXX,
        XXXXXXXX,
        XXXXXXXX

• XXXXXXXX, - Number, required. Must be exactly 8 numbers of 8-characters each.

Example:

.defchr 333333333,
        300000003,
        300000003,
        300000003,
        300000003,
        300000003,
        300000003,
        333333333

Output:

00000000  ff 01 01 01 01 01 01 ff  ff 01 01 01 01 01 01 ff  |................|
00000010

Read more about PPU pattern tables here.

Try it:

.dephase

End a .phase block. Labels defined after .dephase revert to their physical load address. A bank or segment switch (.prg, .chr, .segment) also ends any active phase.

Usage:

.dephase

.dw

Define 16-bit word(s).

Usage:

.dw NUMBER[, NUMBER, ...]

• NUMBER - Number, required. At least one number is required.
• , NUMBER, ... - Number(s), optional. Additional comma-separated numbers may be used.

Example:

.dw $1234, $45678

Output:

00000000  34 12 78 56                                       |4.xV|
00000004

Try it:

.else

Else condition of an .if/.ifdef/.ifndef statement.

Usage:

.else

Example:

.ifdef SOMETHING
    STA $00
.else
    STA $01
.endif

.endenum

End .enum.

Usage:

.endenum

Example:

.enum $0080

TEST_0 .rs 1
TEST_1 .rs 2
TEST_2 .rs 1

.endenum

.endif

End .if/.ifdef/.ifndef statement.

Usage:

.endif

Example:

.ifdef SOMETHING
    STA $00
.else
    STA $01
.endif

.endm

End .macrodef.

Usage:

.endm

Example:

.macrodef TEST_MACRO
    LDA #\1
    STA <\2
.endm

See the section on Macros for more information.

.enum

Start enumerated variable declarations.

Usage:

.enum START[, INC]

• START - Number, required. Value at which to start enumerating.
• , INC - Number, optional. Amount to increment after each enumeration.

Example:

.enum $0080

TEST_0 .rs 1
TEST_1 .rs 2
TEST_2 .rs 1

.endenum

.fill

Fill with bytes.

Usage:

.fill COUNT[, VALUE]

• COUNT - Number, required. Number of bytes to fill.
• , VALUE - Number, optional. Value of each byte. Defaults to $FF.

Example:

.fill 16

Output:

00000000  ff ff ff ff ff ff ff ff  ff ff ff ff ff ff ff ff  |................|
00000010

Try it:

.font

Generate font character tile.

Usage:

.font START[, END]

• START - Character/number, required. Starting ASCII character or code.
• [, END] - Character/number, optional. Ending ASCII character or code. If included, all font tiles from START to [, END] (inclusive) will be generated.

Example:

.font 'A', 'G'

Output:

00000000  38 44 7c 44 44 44 44 00  38 44 7c 44 44 44 44 00  |8D|DDDD.8D|DDDD.|
00000010  78 44 78 44 44 44 78 00  78 44 78 44 44 44 78 00  |xDxDDDx.xDxDDDx.|
00000020  38 44 40 40 40 44 38 00  38 44 40 40 40 44 38 00  |8D@@@D8.8D@@@D8.|
00000030  78 44 44 44 44 44 78 00  78 44 44 44 44 44 78 00  |xDDDDDx.xDDDDDx.|
00000040  7c 40 70 40 40 40 7c 00  7c 40 70 40 40 40 7c 00  ||@p@@@|.|@p@@@|.|
00000050  7c 40 70 40 40 40 40 00  7c 40 70 40 40 40 40 00  ||@p@@@@.|@p@@@@.|
00000060  3c 40 4c 44 44 44 38 00  3c 40 4c 44 44 44 38 00  |<@LDDD8.<@LDDD8.|
00000070

Read more about PPU pattern tables here.

Try it:

.hibytes

Output only the high byte of 16-bit word(s).

Usage:

.hibytes NUMBER[, NUMBER]

• NUMBER - Number, required. At least one number is required.
• , NUMBER, ... - Number(s), optional. Additional comma-separated numbers may be used.

Example:

.hibytes $1234, $5678

Output:

00000000  12 56                                             |.V|
00000002

Try it:

.if

Test if condition.

Can be accompanied by an .else and must be accompanied by an .endif.

Usage:

.if CONDITION

• CONDITION - Condition, required. The code that follows will be processed if the condition is true. See Comparison Operators.

Example:

.if SOMETHING == $01
    LDA #$01
.endif

.ifdef

Test if variable is defined.

Can be accompanied by an .else and must be accompanied by an .endif.

Usage:

.ifdef VARIABLE

• VARIABLE - Variable/constant/etc., required. The code that follows will be processed if the variable has been defined.

Example:

.ifdef SOMETHING
    STA $00
.else
    STA $01
.endif

.ifndef

Test if variable has not been defined.

Can be accompanied by an .else and must be accompanied by an .endif.

Usage:

.ifndef VARIABLE

• VARIABLE - Variable/constant/etc., required. The code that follows will be processed if the variable has not been defined.

Example:

.ifndef SOMETHING
    STA $01
.else
    STA $00
.endif

.incbin

Include binary file.

Usage:

.incbin "FILENAME"[, OFFSET[, LIMIT]]

• "FILENAME" - Path to file, required. Must be within quotes.
• [, OFFSET - File offset index, optional. Index at which to start including binary file.
• [, LIMIT]] - Limit in bytes, optional. Number of total bytes to include.

Example:

.incbin "file.bin"

.include

Include assembly file.

Usage:

.incbin "FILENAME"

• "FILENAME" - Path to file, required. Must be within quotes.

Example:

.include "file.asm"

Included files share a global state with other included files and the main entry point file. That means if a variable is defined in one file, it is available to all other files, provided that they are included after the definition.

Relative filenames in .include — and in every filename-based directive (.incbin, .incpng, .incpal, .incrle, .incwav, .inestrn) — are resolved relative to the directory of the file that contains the directive. A file included from a subdirectory therefore resolves its own includes and assets from that subdirectory, not from the top-level project directory. A path prefixed @/ is the escape from this: see Project-root-relative paths below.

Declaring a filename argument

Any filename argument may be written with a file:// prefix, which declares that the string names an input file:

.incbin "file://logo.chr"
.include "file://defs.asm"

The prefix is stripped before the path is used, so the two spellings load exactly the same file — file:// adds information about the argument rather than changing it. It is a marker, not a URL scheme: there is no host part and no percent-decoding, and file:///path/to/logo.chr is simply the absolute spelling.

The declaration earns its keep on a custom pseudo-instruction, where the assembler otherwise cannot tell that a string is a path. On the built-in directives above it is accepted, harmless, and redundant — their arguments are already known to be filenames — but it lets you write every path in a project the same way. Editors make a declared path clickable either way.

Project-root-relative paths

A filename argument beginning @/ resolves from the project root instead of the containing file's directory:

.include "@/lib/macros.asm"
.incbin  "@/assets/logo.chr"
.incpng  "@/art/tiles.png"

@/lib/macros.asm names the same file no matter which directory the .include sits in — copying that line into a file three levels deeper still finds it, where a relative path would need ../../../lib/macros.asm at that depth and break the moment the file moves again. Everything after the @/ is a path relative to the root:

The project root is found by walking up from the entry file for the nearest .nessemblerc, .nessemblerc.json, or .nessembleignore — the root is the directory containing that marker. A project that already has one of these files gets @/ for free. With no marker anywhere above it, the entry file's own directory is the root, which makes @/foo mean ./foo for a lone source file. The --root CLI flag, and an open editor's workspace folder, both override the walk-up explicitly.

@/ composes with file://: the declaration is stripped first, so "file://@/lib/defs.asm" is a declared, root-relative path — see Declaring a filename argument above and Declaring file arguments for what a custom pseudo-op's script receives.

A @/ path that cannot be resolved is a hard error rather than a silent fallback to file-relative resolution: this happens when no project root can be determined at all (only reachable from the browser playground, which has no filesystem), or when the path climbs back out of the root, e.g. "@/../secret.bin".

.incpal

Include palette from PNG.

Usage:

.incpal "FILENAME"

• "FILENAME" - Path to file, required. Must be within quotes.

Example:

.incpal "palette.png"

The PNG will be scanned, row-by-row/pixel-by-pixel, from the top-left to the bottom-right until it encounters 4 different, but not necessarily unique, colors.

.incpng

Include PNG.

Converts the PNG to CHR tiles. The image must include only 4 colors:

Other colors may be used, but accuracy is not guaranteed.

Usage:

.incpng "FILENAME"

• "FILENAME" - Path to file, required. Must be within quotes.

Example:

.incpng "image.png"

Read more about PPU pattern tables here.

.incrle

Include binary data to be RLE-encoded

The RLE-encoding scheme used is one featured in a few Konami NES titles, known as Konami RLE. The breakdown of bytes:

Usage:

.incrle "FILENAME"

• "FILENAME" - Path to file, required. Must be within quotes.

Read more about NES RLE compression here.

.incwav

Include WAV.

Converts WAV to a 1-bit PCM.

Usage:

.incwav "FILENAME"[, AMPLITUDE]

• "FILENAME" - Path to file, required. Must be within quotes.
• [, AMPLITUDE] - Amplitude, optional. Amplitude of WAV.

Example:

.incwav "audio.wav", 24

.ines2

Emit a NES 2.0 header.

Sets bits 2-3 of Flags 7 to the NES 2.0 identifier (10) and switches the output header from iNES 1.0 to NES 2.0, which widens the mapper (0-4095) and PRG/CHR sizes and repurposes bytes 8-15.

When NES 2.0 mode is active, some existing directives change meaning:

• .inesprg / .ineschr become 12-bit (the byte-9 MSB nibbles are written automatically for counts above 255).
• .inesmap becomes 12-bit (writes byte 8 as well).
• .inesprgram targets the NES 2.0 PRG-RAM field and takes a byte size (not 8 KB units).
• .inestv provides the NTSC/PAL fallback for the .inestiming byte.
• .inesvs / .inespc10 become sugar for the .inesconsole type.

NES 2.0-only directives (.inessubmap, .inesprgnvram, .ineschrram, .ineschrnvram, .inestiming, .inesconsole, .inesvsppu, .inesvshw, .inesmiscrom, .inesexpansion) require this directive.

Usage:

.ines2 FLAG

• FLAG - Number, required. Non-zero to emit a NES 2.0 header.

Example:

.ines2 1

.ines4scr

iNES four-screen VRAM flag.

Sets bit 3 of Flags 6 (the "alternative nametable layout" bit), used by boards that provide four-screen VRAM instead of the hard-wired mirroring selected by .inesmir.

Usage:

.ines4scr FLAG

• FLAG - Number, required. Non-zero to set four-screen VRAM.

Example:

.ines4scr 1

.inesbat

iNES battery / persistent memory flag.

Sets bit 1 of Flags 6, indicating the cartridge contains battery-backed PRG-RAM at $6000-$7FFF (or other persistent memory).

Usage:

.inesbat FLAG

• FLAG - Number, required. Non-zero to indicate persistent memory.

Example:

.inesbat 1

.ineschr

iNES CHR count.

Usage:

.ineschr COUNT

• COUNT - Number, required. Number of CHR banks. In NES 2.0 mode a count above 255 also writes the byte-9 MSB nibble (up to 4095).

Example:

.ineschr 1

.ineschrnvram

NES 2.0 battery CHR-RAM size.

Sets the battery-backed CHR-RAM field (byte 11 bits 4-7) of a NES 2.0 header. Requires .ines2.

Usage:

.ineschrnvram BYTES

• BYTES - Number, required. Size in bytes: 0, or a power-of-two byte count from 128 to 2097152 (stored as the shift count size = 64 << n).

Example:

.ineschrnvram 8192

.ineschrram

NES 2.0 CHR-RAM size.

Sets the volatile CHR-RAM field (byte 11 bits 0-3) of a NES 2.0 header. Requires .ines2.

Usage:

.ineschrram BYTES

• BYTES - Number, required. Size in bytes: 0, or a power-of-two byte count from 128 to 2097152 (stored as the shift count size = 64 << n).

Example:

.ineschrram 8192

.inesconsole

NES 2.0 console type.

Sets bits 0-1 of Flags 7. Requires .ines2. This is the canonical form of .inesvs (value 1) and .inespc10 (value 2); setting a conflicting combination is an error.

Value 3 (extended console type) is not yet supported.

Usage:

.inesconsole NUMBER

• NUMBER - Number, required. Console type (0-3).

Example:

.inesconsole 1

.inesexpansion

NES 2.0 default expansion device.

Sets byte 15 (bits 0-5) of a NES 2.0 header. Requires .ines2.

Usage:

.inesexpansion NUMBER

• NUMBER - Number, required. Expansion device (0-63).

Example:

.inesexpansion 1

.inesmap

iNES mapper number.

Usage:

.inesmap NUMBER

• NUMBER - Number, required. Mapper number. iNES supports 0-255; in NES 2.0 mode the range widens to 0-4095 (byte 8 holds the high nibble). A value above 255 requires .ines2.

Read more about NES mappers here.

.inesmir

iNES mirroring.

Sets bit 0 of Flags 6, the hard-wired nametable arrangement. The other Flags 6 bits are controlled by their own directives: .inesbat (battery), .inestrn (trainer), and .ines4scr (four-screen VRAM).

xxxxxxx0
       |
       +- Mirroring: 0: horizontal (vertical arrangement)
                     1: vertical (horizontal arrangement)

Usage:

.inesmir NUMBER

• NUMBER - Number, required. Mirroring type.

.inesmiscrom

NES 2.0 miscellaneous ROM count.

Sets byte 14 (bits 0-1) of a NES 2.0 header, the number of miscellaneous ROMs present. Requires .ines2.

Usage:

.inesmiscrom NUMBER

• NUMBER - Number, required. Number of miscellaneous ROMs (0-3).

Example:

.inesmiscrom 1

.inespc10

iNES PlayChoice-10 flag.

Sets bit 1 of Flags 7, marking the ROM as a PlayChoice-10 title. This bit is not part of the official specification and most emulators ignore it. In NES 2.0 mode this is sugar for .inesconsole type 2.

Only the header bit is set. The optional 8 KB PlayChoice INST-ROM and PROM data sections are not emitted.

Usage:

.inespc10 FLAG

• FLAG - Number, required. Non-zero to mark a PlayChoice-10 title.

Example:

.inespc10 1

.inesprg

iNES PRG count.

Usage:

.inesprg COUNT

• COUNT - Number, required. Number of PRG banks. In NES 2.0 mode a count above 255 also writes the byte-9 MSB nibble (up to 4095).

Example:

.inesprg 1

.inesprgnvram

NES 2.0 battery PRG-RAM size.

Sets the battery-backed PRG-RAM field (byte 10 bits 4-7) of a NES 2.0 header. Requires .ines2.

Usage:

.inesprgnvram BYTES

• BYTES - Number, required. Size in bytes: 0, or a power-of-two byte count from 128 to 2097152 (stored as the shift count size = 64 << n).

Example:

.inesprgnvram 8192

.inesprgram

iNES / NES 2.0 PRG-RAM size.

In iNES mode, sets byte 8 of the header, the size of PRG-RAM in 8 KB units (a value of 0 infers 8 KB for compatibility).

In NES 2.0 mode, sets the volatile PRG-RAM field (byte 10 bits 0-3) and the argument is a byte size instead — pair it with .inesprgnvram for battery-backed PRG-RAM.

Usage:

.inesprgram SIZE

• SIZE - Number, required. In iNES mode, PRG-RAM size in 8 KB units. In NES 2.0 mode, a byte size: 0, or a power-of-two byte count from 128 to 2097152 (stored as the shift count size = 64 << n).

Example:

.inesprgram 1

.inessubmap

NES 2.0 submapper number.

Sets byte 8 (bits 4-7) of a NES 2.0 header, the submapper that distinguishes variants of a mapper. Requires .ines2.

Usage:

.inessubmap NUMBER

• NUMBER - Number, required. Submapper number (0-15).

Example:

.inessubmap 1

.inestiming

NES 2.0 CPU/PPU timing.

Sets byte 12 of a NES 2.0 header, the region timing. Requires .ines2. When unset, .inestv provides the NTSC/PAL value.

Usage:

.inestiming NUMBER

• NUMBER - Number, required. Timing (0-3).

Example:

.inestiming 0

.inestrn

iNES trainer include.

The assembled trainer must be no larger than 512 (0x200) bytes. The appropriate flag is automatically set in the iNES header to indicate a trainer is present.

Usage:

.inestrn "FILENAME"

• "FILENAME" - Path to file, required. Must be within quotes.

Example:

.inestrn "trainer.asm"

.inestv

iNES TV system.

Sets bit 0 of Flags 9, the TV system the ROM targets. PAL is also mirrored into the unofficial Flags 10 TV-system field (bits 0-1: 0 NTSC, 2 PAL) that some emulators honor. In NES 2.0 mode this instead provides the NTSC/PAL fallback for the .inestiming byte.

xxxxxxx0
       |
       +- TV system: 0: NTSC
                     1: PAL

Usage:

.inestv SYSTEM

• SYSTEM - Number, required. 0 for NTSC, 1 for PAL.

Example:

.inestv 1

.inesvs

iNES VS Unisystem flag.

Sets bit 0 of Flags 7, marking the ROM as a VS Unisystem arcade title. In NES 2.0 mode this is sugar for .inesconsole type 1.

Usage:

.inesvs FLAG

• FLAG - Number, required. Non-zero to mark a VS Unisystem title.

Example:

.inesvs 1

.inesvshw

NES 2.0 VS System hardware type.

Sets byte 13 (bits 4-7) of a NES 2.0 header. Only meaningful when the .inesconsole type is VS (1); ignored otherwise. Requires .ines2.

Usage:

.inesvshw NUMBER

• NUMBER - Number, required. VS System hardware type (0-15).

Example:

.inesvshw 0

.inesvsppu

NES 2.0 VS System PPU type.

Sets byte 13 (bits 0-3) of a NES 2.0 header. Only meaningful when the .inesconsole type is VS (1); ignored otherwise. Requires .ines2.

Usage:

.inesvsppu NUMBER

• NUMBER - Number, required. VS System PPU type (0-15).

Example:

.inesvsppu 0

.lobytes

Output only the low byte of 16-bit word(s).

Usage:

.lobytes NUMBER[, NUMBER]

• NUMBER - Number, required. At least one number is required.
• , NUMBER, ... - Number(s), optional. Additional comma-separated numbers may be used.

Example:

.lobytes $1234, $5678

Output:

00000000  34 78                                             |4x|
00000002

Try it:

.macro

Call macro.

Usage:

.macro MACRO[, NUMBER, ...]

• MACRO - Name, required. Name of previously-defined macro.
• , NUMBER, ... - Number(s), optional. Additional comma-separated numbers may be used.

Example:

.macro TEST_MACRO

See the section on Macros for more information.

.macrodef

Start macro definition.

Usage:

.macrodef MACRO
    CODE...
.endm

• MACRO - Name, required. Name of macro.
• CODE... - Code, required. Assembly code.

Example:

.macrodef TEST_MACRO
    LDA #\1
    STA <\2
.endm

See the section on Macros for more information.

.org

Organize code.

Set the address of the current bank in which to start organizing code.

Usage:

.org ADDRESS

Example:

.org $C000

.phase

Assemble code for a different run-time address.

When a PRG bank is swapped in at a different address than the one it is laid out at, the address labels receive (its .org) does not match where the code actually runs. .phase ADDRESS overrides the address labels receive so it reflects the run-time (post-swap) location, while ROM layout keeps flowing from .org unchanged. This removes the need to subtract the swap offset from every label by hand.

The override stays in effect until .dephase or a bank/segment switch (.prg, .chr, .segment). It applies only to symbol values; branch targets and emitted bytes are unaffected, since the offset cancels in any address difference.

Usage:

.phase ADDRESS

• ADDRESS - Number, required. The run-time address the current location maps to.

Example:

.prg 1
.org $C000       ; laid out at $C000 in ROM
.phase $8000     ; but swapped in at $8000 at run time

label_def:       ; label_def == $8000
    NOP
    JMP label_def

.dephase

.prg

Set PRG bank index.

Usage:

.prg NUMBER

• NUMBER - Number, required. PRG bank index.

Example:

.prg 0

PRG banks are 4K bytes (0x4000) in size.

.random

Output random byte(s).

The algorithm for the PRNG is the suggested POSIX implementation of rand().

Usage:

.random [SEED[, COUNT]]

• [SEED - Number or string, optional. Seeds the random number generator. Defaults to the current system time.
• [, COUNT]] - Number of bytes to output, optional. Defaults to 1.

Example:

.random "Secret Key", 16

.rsset

Set initial value for .rs declarations.

Usage:

.rsset ADDRESS

• ADDRESS - Number, required. Address to start .rs declarations.

Example:

.rsset $0000

.rs

Reserve space for variable declaration.

Usage:

VARIABLE .rs NUMBER

• VARIABLE - Variable name, required. Name of variable to declare.
• NUMBER - Number (in bytes) to reserve, required.

Example:

.rsset $0000

label_01 .rs 1
label_02 .rs 2
label_03 .rs 1

.db label_01, label_02, label_03

Output:

00000000  00 01 03                                          |...|
00000003

Try it:

.segment "SEGMENT[0-9]+"

.segment "PRG1"

.ease FUNCTION[, START[, END[, STEPS]]]

.ease "easeOutBounce", 0, $20, $40

00000000  00 00 00 00 00 01 02 02  03 04 06 07 08 0a 0b 0d  |................|
00000010  0f 11 13 16 18 1a 1d 1f  1e 1d 1c 1b 1a 19 19 18  |................|
00000020  18 18 18 18 18 18 18 19  19 1a 1b 1c 1d 1e 1f 1f  |................|
00000030  1e 1e 1e 1e 1e 1e 1e 1e  1f 1f 1f 1f 1f 1f 1f 20  |............... |
00000040

.macrodef TEST_MACRO
    LDA #$00
    STA $2005
    STA $2005
.endm

.macro TEST_MACRO

00000000  a9 00 8d 05 20 8d 05 20                           |.... .. |
00000008

.macrodef TEST_MACRO
    LDA #\1
    STA \2
    STA \2
.endm

.macro TEST_MACRO, $00, $2005

.macrodef TEST_MACRO
    LDA #\1
    STA \2
    STA \2
.endm

.macro TEST_MACRO, $00, $2005

.macrodef COUNT_PARAMS
    .db \#
.endm

.macro COUNT_PARAMS, $01, $01, $01

00000000  03                                                |.|
00000001

.macrodef TEST_MACRO
    LDX #$08
label_\@:
    DEX
    BNE label_\@:
.endm

.macro TEST_MACRO
.macro TEST_MACRO
.macro TEST_MACRO

00000000  a2 08 ca d0 fd a2 08 ca  d0 fd a2 08 ca d0 fd     |...............|
0000000f