PROMbased

PROM-based refers to hardware or systems that rely on Programmable Read-Only Memory (PROM) to store firmware or control logic. PROM is a type of non-volatile memory that is programmed once, after which its contents cannot be altered except by replacing the device. In PROM-based designs, firmware, microcode, or lookup tables are physically embedded in PROM devices on the circuit board.

Unlike flash or EEPROM, PROM is one-time programmable. It is typically programmed by a dedicated PROM programmer that fuses or blows internal links to encode the data. After programming, the memory is read-only for the lifetime of the device. This provides tamper resistance and deterministic behavior but sacrifices post-production flexibility.

PROM-based solutions were common in early microcomputers, embedded controllers, and arcade/video game hardware. They offered low unit costs for small production runs and simplified firmware distribution because the firmware was fixed at manufacture. As memory technology evolved, EPROM, EEPROM, and flash memory replaced PROM in most new designs.

Limitations include one-time programming, limited storage density, and the need to replace the component to update firmware. They typically require separate programming steps during assembly or service, adding manufacturing flow constraints. In modern devices, PROM-based implementations are largely confined to legacy equipment, specialized systems, or niche applications where immutability is desired.

In some contexts, the phrase PROM-based is used to emphasize firmware that cannot be changed in the field, reinforcing security and reproducibility.