PROM

What does PROM mean?

Programmable read-only memory (PROM) is a type of Non-Volatile Memory that can be programmed once with a specific pattern of data. Unlike read-only memory (ROM), which is pre-programmed by the manufacturer, PROM allows users to customize the data stored on the Chip. This makes PROM ideal for applications that require the Storage of fixed data, such as firmware images or lookup tables.

PROMs are typically programmed using a special device called a PROM programmer. The programmer connects to the PROM chip and transfers the desired data pattern to the chip’s memory cells. Once the programming process is complete, the data stored on the PROM cannot be altered or erased. However, some PROMs can be reprogrammed a limited number of times using a special technique called electric field programming (EFP).

PROM technology is based on the use of fusible links to permanently alter the electrical properties of memory cells. Each memory cell in a PROM chip consists of a transistor and a fusible link. When the PROM is programmed, a high-voltage pulse is sent through the fusible link, which causes it to rupture. This effectively disconnects the transistor from the cell, preventing it from conducting electricity. By selectively blowing the fusible links, the desired data pattern can be programmed into the PROM chip.

Applications

PROM is used in a wide variety of applications, including:

• Firmware storage: PROMs are commonly used to store firmware images for electronic devices such as computers, printers, and modems. Firmware is a type of software that is stored on a non-volatile memory chip and contains the instructions necessary for the device to operate.
• Lookup tables: PROMs can be used to store lookup tables for applications such as address decoding, character generation, and color palette translation. Lookup tables are arrays of data that are used to quickly retrieve information based on a given input value.
• Data Storage: PROMs can be used to store small amounts of data in applications where data retention is critical. Examples include Configuration data for electronic devices and calibration data for sensors.

History

The development of PROM technology began in the early 1950s with the invention of the magnetic core memory. Magnetic core memory was a type of non-volatile memory that used magnetic cores to store data. However, magnetic core memory was large, expensive, and power-hungry. In the late 1950s, researchers at Texas Instruments developed the first practical PROM chip. This chip was based on the use of fusible links to alter the electrical properties of memory cells.

The first PROMs were relatively small, with capacities of only a few hundred bits. However, PROM technology rapidly evolved in the 1960s and 1970s. By the mid-1970s, PROMs with capacities of several kilobits were available. This made PROMs a viable option for a wider range of applications.

In the 1980s, PROM technology was largely replaced by EEPROM (Electrically Erasable Programmable Read-Only Memory) technology. EEPROMs are a type of non-volatile memory that can be both programmed and erased electrically. This makes EEPROMs much more versatile than PROMs. However, PROMs are still used in some applications where data retention is critical and programming time is not an issue.