Erasable Programmable Read Only Memory
EPROM is a type of ROM memory chip. ROM memory is a type of integrated circuit containing a program inside. This program cannot be modified during its usage, hence the name ”read-only“. Another characteristic of ROM memories is that their contents aren’t lost when the power goes off, contrary to what happens to RAM memories.
The ROM memory chip is sold ”virgin“ and the program is recorded through an appropriate recorder. It is possible to erase the chip to record a new program. To erase it you must expose the chip to ultraviolet light during some time (15 to 45 minutes, depending on how old the chip is). This chip has a small window on top of it to allow it to be erased. After erasing its contents, the memory is ”virgin“ again.
EPROM chip must be removed from the circuit for both erasing and programming.
Figure 1: Two EPROM chips. Notice the erase window.