Programmable read-only memory

Programmable read-only memory (PROM) refers to a type of ROM which can be written using a PROM programmer. This is an alternative to traditional ROM chips, which are normally mass-produced.

Description
The contents of each bit in a PROM is determined by a or. The memory can be programmed once after manufacturing by "blowing" the fuses, which is an irreversible process. Blowing a fuse opens a connection while blowing an antifuse closes a connection (hence the name). Programming is done by applying high-voltage pulses which are not encountered during normal operation. An alternative to earlier fuses are s, which are used in smaller production runs of Programmable Array Logic chips.