Introduction to Programmable Read Only Memory PROM

The core of the electronic enthusiast network: Programmable read-only memory PROM is an early PLD, is a simple PLD. Electronic enthusiast network Xiaobian brings everyone to understand what is the invention process of PROM, PROM and the classification of PROM.

What is a PROM?

PROM, an abbreviation for Programmable read-only memory, means programmable read-only memory. PROM is a simple programmable logic device (PLD). Early programmable logic devices were only programmable read only memory (PROM), ultraviolet light can be replaced by read only memory (EPROM) and electrically erasable read only memory (EEPROM). Due to structural constraints, they can only perform simple digital logic.

PROM's invention process

Programmable read-only memory was invented by Zhou Wenjun in 1956, and Zhou Wenjun worked at American Paula Emma in Garton City, New York. The invention was proposed by the US Air Force to enhance the flexibility and security of Air Force computers and Atlas E/F-band missiles.

PROM classification

PROM is divided into three main categories: ROM, EPROM and E2PROM.

1. One-time programming read-only memory (ROM): Programmable read-only memory is only allowed to be written once, so it is also called "One TIme Progarmming ROM" (OTP-ROM). When the PROM is shipped from the factory, the stored contents are all 1. The user can write some of the units to the data 0 as needed (some of the PROMs are all 0 at the factory, then the user can write some of them to 1) To achieve its purpose of "programming". The typical product of PROM is “bipolar fuse structure”. If we want to rewrite some units, we can give these units enough current and maintain a certain time, the original fuse can be blown, so The effect of rewriting some bits has been achieved. Another type of classic PROM is a PROM using a "Schottky diode". When the diode is turned off in the factory, the reverse voltage is applied to the "Schottky diode" by a large current method. Permanent breakdown can be.

2. UV erase programmable read only memory (EPROM): is a computer storage chip that can retain data after power off - that is, non-volatile (non-volatile). It is a set of floating gate transistors that are individually programmed by an electronic device that provides a higher voltage than the voltages commonly used in electronic circuits. Once programmed, the EPROM can only be erased with strong UV radiation. The EPROM is easily identified by the transparent window on the top of the package where the silicon wafer is visible. This window is also used for UV erasure.

3. Electrically Erasable Programmable Read Only Memory (E2PROM): A memory chip that does not lose data after power down. The EEPROM can erase existing information and reprogram it on a computer or on a dedicated device. Generally used in plug and play.

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