ROM Types – Explained
ROMs is a read-only memory, used in computers and other electronic devices. You’ll find ROM chips in computers and other types of electronic products like VCRs, game consoles, and car radios. There are different variations on the classic ROM chips that were produced by the manufacturer and could not change. The most common types of ROM memory are:
ROM (MROM) Mask
MROM is short for Read Only Memory Mask. It is inexpensive and is the first ROM that is a hardwired device that contains a preprogrammed set of data or instructions.
Programmable ROM (PROM)
This type of ROM can be reprogrammed using a special device called a PROM programmer. In general, a PROM can only be changed/updated once.
Erasable Programmable Read Only Memory (EPROM)
This type of ROM can have its contents erased by UV light and then reprogrammed by an RPROM programmer. This procedure can be carried out many times; however, constant erasing and rewriting will eventually render the chip useless.
Electrically Erasable Programmable Read Only Memory (EEPROM)
EEPROMs are used to store the BIOS of a computer system and can be updated without returning the unit to the factory. The EEPROM can be programmed and erased about 10,000 times by exposing it to an electrical charge, so a transparent window is not needed. Both erasing and programming take between 4 and 10 milliseconds.
Flash memory (flash) is a modern type of EEPROM. Flash memory can be erased and rewritten faster than ordinary EEPROM, and newer designs have very high endurance characteristics, with cycles in excess of 1,000,000.
Electrically modifiable read-only memory (EAROM)
EARM is a form of semiconductor memory in which the contents of selected memory locations can be changed by applying suitable electrical signals. Normally these changes are infrequent.
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