What Is Programmable Read Only Memory?

Programmable read-only memory, abbreviated PROM or FPROM, is a computer memory chip that allows data to be written to the device using hardware called a PROM programmer. After the PROM is programmed, it can only use those data, and it cannot be reprogrammed to use this memory for permanent storage of programs. It is often used in products with translatable languages such as electronic game consoles or electronic dictionaries.

Programmable read-only memory, abbreviated PROM or FPROM, is a computer memory chip that allows data to be written to the device using hardware called a PROM programmer. After the PROM is programmed, it can only use those data, and it cannot be reprogrammed to use this memory for permanent storage of programs. It is often used in products with translatable languages such as electronic game consoles or electronic dictionaries.

Chinese name

Programmable read-only memory

Foreign name

Programmableread-only memory

Introduction to programmable read-only memory

classification

1. One-time-programmable read-only memory (ROM) Programmable read-only memory can only be written once, so it is also known as "One Time Progarmming ROM" (OTP-ROM). When PROM is shipped from the factory, the stored content is all 1. Users can write some of these units into data 0 according to their needs. (Some PROMs have all 0 data when they leave the factory, so users can write some of them into 1.) To "program" it. PROM's typical product is a "bipolar fuse structure". If we want to rewrite some units, we can pass a sufficient current to these units and maintain a certain time, the original fuse can be blown, so Reached the effect of rewriting some bits. Another type of classic PROM is a PROM that uses a "Schottky diode". When it leaves the factory, the diodes are in the reverse cut-off state, or the reverse voltage is applied to the "Schottky diode" by a large current method, which causes Permanent breakdown is sufficient.

2. Ultraviolet erasable programmable read-only memory (EPROM) can erase the original information with ultraviolet rays, and can rewrite new information.

3. Electrically erasable programmable read-only memory (E2PROM)

Programmable read-only memory invention process

Programmable read-only memory was invented by Zhou Wenjun in 1956. Zhou Wenjun worked at American Emma Corporation in Caton City, New York. This invention was proposed by the United States Air Force to improve the flexibility and security of Air Force computers and Atlas E / F band missiles.

Programmable read-only memory principle

The overall structure, working principle and usage of PROM are the same as those of mask ROM (see read-only memory). The difference is that when the PROM device is shipped from the factory, diodes are set at each crossing point of the memory matrix, and fast fuses are connected in series with the diodes, as shown in the figure.

figure 1

Users can write data according to their own needs, that is, programming PROM. When programming, fuses that are not connected in series with the diodes should be blown. For this reason, a sufficiently large pulse current must be passed between the corresponding word line and bit line. Programming is usually done with a special programmer.

Because the fuse cannot be recovered after the fuse is blown, the PROM produced by the fuse process cannot be modified once data is written.

PROM is produced in batches. When the amount of ROM required is small, using PROM is more economical than making a special mask ROM, and it is beneficial to shorten the production cycle.