Click a button name, then press the key to bind. Esc cancels.

Undocumented opcodes are side effects of the 6502 design that the manufacturer never documented (LAX, SAX, DCP, ISC, SLO, RLA, SRE, RRA and others). A few games and test programs use them. Leave this on "Official opcodes only" unless a game needs the extras. With official-only mode, running an undocumented opcode halts the CPU.

Emulation speed (0.1 to 10):

x

Audio is muted while the speed is not 1x.

History length: 10 seconds 30 seconds 60 seconds 120 seconds

No history yet.

Hold Backspace (or the Rewind toolbar button) to rewind. Drag the timeline to jump to a point, then press Run to continue from there.

Code: Name: Add

Format: AAAA:VV writes hex value VV to address AAAA every frame. AAAA:VV?CC only writes while the byte currently equals CC. Addresses must be in work RAM ($0000-$1FFF) or cartridge RAM ($6000-$7FFF). Cheats never change the ROM and are not part of save states.