6502

JavaScript utilities for 6502 programming.

Installation

npm install @neshacker/6502-tools

Assembler

The package includes a basic 6502 assembler with support for basic variable assignment, a handful of assembler commands, and all core 6502 instruction addressing modes.

The assembler is very early in development and is not fully featured but it does work well for some basic tasks, such as converting assembly to hex-strings for use with a hex editor, etc. For larger tasks or projects please use a more mature assembler such as ca65.

API Reference

Assembler.inspect(source)

Parses and assembles the given source into a linear intermediate representation then outputs the results of the parse to the console.

const { Assembler } = require('@neshacker/6502-tools')
const source = `
  my_routine = $ACDC
  .org $BD17
  another_routine:
    lda #22
    jsr my_routine
    rts
`
// Assemble and inspect the source
Assembler.inspect(source)

BD17 another_routine:
BD17 A916        lda #22
BD19 20DCAC      jsr my_routine
BD1C 60          rts

Assembler.inspectFile(path)

Same as Assember.inspect but instead converts the source found in the file with the given path.

Assembler.toHexString(source)

Converts the given assembly source into a string of hexadecimal digits for use with a hex editor.

const { Assembler } = require('@neshacker/6502-tools')
const source = `
  my_routine = $ACDC
  .org $BD17
  another_routine:
    lda #22
    jsr my_routine
    rts
`
// Assemble and inspect the source
Assembler.toHexString(source)

A91620DCAC60

Assembler.fileToHexString(source)

Same as Assembler.toHexString but instead converts the source found in the file with the given path.

Commands

.addr

This command set the absolute program address at the point of invocation. It is useful for defining patch segements for ROM hacks.

; Set the absolute program offset to $C000
.org $C000
  lda #0      ; Address $C000
  @loop:      ; Address = $C002
  dex         ; Address = $C002
  bne @loop   ; Address = $C003, branch to @loop on zero flag

.byte

This defines a run of arbitrary bytes to be processed by the assembler. Useful for defining lookup tables or text segments.

.byte 16, 32, 64   ; Literal bytes: $10, $20, $40
.byte "Hello"      ; Literal bytes: $48, $65, 6C, $6C, $6F

License

MIT