What Are The Variations Of Rom Chips?

ROM chips (Read Only Memory) are devices designed to hold data in an embedded system. This could be executable code or any other data necessary. Types of ROM are classed by the methods used to add the data to them. There is masked ROM where the data is added during the manufacturing process. The advantage to masked parts is they are very cheap. The disadvantage is that they are not modifiable. Next there is a PROM (Programmable Read Only Memory). These are user programmable but only one time. They are sometimes called OTP PROM (One Time Programmable). Next EPROM (erasable-and-programmable ROM) are programmed like PROMs however they can be erased some number of times. They are usually erased by exposing them to ultra-violet light thru a window on top of the chip. EEPROMs are electrically-erasable-and-programmable. EEPROMs can be electronically erased and reprogrammed one byte at a time.

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