Phosphoneo for beginners
An emulator is a program that pretends to be a machine. This one pretends to be a Neo6502, a small retro board, so that programs can be tried without the board.
The board and its double
The Neo6502 is an 80 × 55 mm board that pairs a real 65C02 processor (the kind found in 1980s 8-bit computers) with an RP2040 microcontroller. The 65C02 runs programs; the RP2040 does everything else: it draws on screen, plays sounds, reads files and the keyboard. That part is called the firmware.
Phosphoneo reproduces this whole in a PC program. You give it a Neo6502 program; it runs it as the board would, and you see the screen in a window, or record what it displays.
Why not just use the board?
Because a trial on the board means plugging it in, copying the program, and watching the screen by eye. With Phosphoneo, a trial fits in one command line, gives the same result every time, and fits into a test script. You can make it type on the keyboard, move the gamepad, take a photo of the screen at the cycle you want, or film a game.
Three words to know
- Cycle: the processor’s heartbeat. Phosphoneo counts time in cycles: 6,250,000 cycles make one second of machine time. This is what makes its trials repeatable.
- Firmware: the RP2040’s program. Phosphoneo does not imitate it: it runs its code.
- Reference screenshot: an image taken by the emulator and kept as proof. If a change alters a single pixel, a test sees it.
What next?
The first launch shows the three basic commands; the options detail every setting; the recipes combine several options for specific needs.