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read only memory (ROM)

The Read Only Memory (ROM) is a non-volatile memory whose memory content is stored during the manufacturing process and cannot be changed or deleted. The ROM content is retained even after the operating voltage is switched off. ROMs are therefore used for storing programs and data that must be available to the central processing unit continuously and unchanged.

The memory chip developed in 1971 is programmed by the manufacturer. This programming is usually done with the last metallization mask and cannot be changed afterwards. This manufacturing process allows memory chips to be prefabricated down to the last metallization step. Subsequent modification of the stored data is not possible.

Memory technologies used in memory devices

Memory technologies used in memory devices

However, there are ROMs that can be programmed by the user, the Programmable Read Only Memories( PROM), and those where the programming can be undone.

EPROM with erase window, photo: Wombat

EPROM with erase window, photo: Wombat

This can be done by irradiation with UV light or by an electrical pulse. These versions are called Erasable PROM( EPROM), and Electrically Erasable PROM( EEPROM).

Informations:
Englisch: read only memory - ROM
Updated at: 03.03.2017
#Words: 169
Links: non-volatile memory (NVM), content, process, voltage, data
Translations: DE
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