# programmable read-only memory

> form of digital memory that can be written once by blowing fuses/antifuse to set bits

**Wikidata**: [Q381364](https://www.wikidata.org/wiki/Q381364)  
**Wikipedia**: [English](https://en.wikipedia.org/wiki/Programmable_ROM)  
**Source**: https://4ort.xyz/entity/programmable-read-only-memory

## Summary
Programmable read-only memory (PROM) is a form of digital memory designed to be written only once. This programming is achieved by physically altering the memory cells, typically by blowing fuses or antifuses to set the bits. Once programmed, the data stored in PROM cannot be modified, making it a permanent storage solution.

## Key Facts
*   PROM is a form of digital memory that can be written once.
*   Programming PROM involves blowing fuses or antifuses to set its bits.
*   It is classified as a "write once read many" data storage device, meaning information, once written, cannot be modified.
*   PROM is a type of non-volatile random-access memory, retaining its information even when power is turned off.
*   The 539 series integrated circuits from the Soviet Union represent a single model of user-programmable diode matrix ROM.
*   It is also categorized under "One Time Programmable" memory.
*   Aliases for programmable read-only memory include PROM, FPROM, P-ROM, and Programmable Read Only Memory.
*   An image example is available showing an ANT Nachrichtentechnik DBT-03 with a Texas Instruments TBP18SA030N chip.

## FAQs
### Q: What is programmable read-only memory (PROM)?
A: Programmable read-only memory (PROM) is a type of digital memory that can be written to only once. Its programming involves physically altering the memory cells, typically by blowing fuses or antifuses to permanently set the bits.

### Q: Can data stored in PROM be changed or erased?
A: No, data stored in PROM cannot be changed or erased once it has been written. It is a "write once read many" device, meaning the information is permanently set after the initial programming.

### Q: Is PROM volatile or non-volatile memory?
A: PROM is a non-volatile random-access memory. This means it retains its stored information even when the power supply is turned off, unlike volatile memory types such as DRAM and SRAM.

### Q: How is PROM programmed?
A: PROM is programmed by a process that involves blowing tiny fuses or creating antifuses within the memory cells. This physical alteration permanently sets the state of each bit, making the data unchangeable thereafter.

## Why It Matters
Programmable read-only memory (PROM) is significant because it provides a permanent, non-volatile storage solution for critical data and instructions that must not be altered after initial programming. Its "write once" characteristic ensures data integrity and security, making it ideal for applications where firmware, boot-up instructions, or configuration settings need to be fixed and immutable. As a non-volatile memory, PROM retains its information without power, which is crucial for devices that need to start up reliably with pre-defined instructions. This combination of permanence and non-volatility allows for the creation of robust and dependable electronic systems, ensuring that essential operational code or data remains intact regardless of power cycles or potential tampering. It serves as a foundational technology for embedding unchangeable software into hardware.

## Notable For
*   Being a "write once" digital memory, programmed by physically blowing fuses or antifuses to set bits, making the stored data permanent.
*   Its classification as a "write once read many" data storage device, ensuring that once information is written, it cannot be modified.
*   Functioning as a non-volatile random-access memory, meaning it retains its stored information even when power is turned off.
*   Including specific historical examples like the Soviet Union's 539 series integrated circuits, which were user-programmable diode matrix ROMs.
*   Being a foundational "One Time Programmable" (OTP) memory technology.

## Body

### Definition and Core Function
Programmable read-only memory (PROM) is a form of digital memory. Its primary characteristic is that it can be written to only once. The process of writing data to a PROM involves physically altering its memory cells, typically by blowing internal fuses or creating antifuses to set the individual bits. Once programmed, the data stored within a PROM is permanent and cannot be modified or erased.

### Classification and Characteristics
*   **Write Once Read Many (WORM):** PROM falls under the category of "write once read many" data storage devices. This classification signifies that information, once written into the memory, becomes immutable and can only be read thereafter.
*   **Non-Volatile Random-Access Memory:** PROM is a type of non-volatile random-access memory. This means it retains its stored information even when the power supply to the device is turned off. This characteristic contrasts with volatile memory types like dynamic random-access memory (DRAM) and static random-access memory (SRAM), which require continuous power to maintain data.
*   **One Time Programmable (OTP):** It is also categorized as an "One Time Programmable" memory, emphasizing its single-write capability.

### Programming Mechanism
The programming of PROM relies on a physical change within the memory chip. Each memory cell contains a fuse or an antifuse. During programming, a high current is passed through specific cells, either blowing the fuse (creating an open circuit) or creating a conductive path in an antifuse (creating a short circuit). This irreversible physical alteration permanently sets the logical state (0 or 1) of the bit.

### Related Entities and Examples
*   **539 Series Integrated Circuits:** A specific historical example includes the 539 series integrated circuits from the Soviet Union. These circuits represented a single model of user-programmable diode matrix ROM.

### Identifiers and Aliases
*   **Aliases:** PROM is known by several aliases, including PROM, FPROM, P-ROM, Memoria programable de sólo lectura, Memoria programable de solo lectura, Programmable Read Only Memory, Programable ROM, ピーロム, プログラマブルROM, and 可編程程式唯讀記憶體.
*   **GND ID:** 4151109-8
*   **LEX ID:** prom
*   **PSH ID:** 12444
*   **KBPedia ID:** ProgrammableReadOnlyMemory (referenced from Q64139102 on 2020-07-09)
*   **Freebase ID:** /m/0d6g7 (referenced from Q15241312 on 2013-10-28)
*   **Treccani ID:** prom (with qualifier PROM)
*   **UNSPSC Code:** 32101604
*   **Microsoft Academic ID (discontinued):** 39496706
*   **Encyclopedia of China (third edition) ID:** 32690
*   **Treccani Vocabulary ID:** prom (with qualifier PROM)
*   **Garzanti Linguistica ID:** PROM (with qualifier PROM)
*   **Treccani's Dizionario delle Scienze Fisiche ID:** prom (published 1996, with qualifier PROM)

### Visual Representation
An image associated with programmable read-only memory depicts an ANT Nachrichtentechnik DBT-03, featuring a Texas Instruments TBP18SA030N chip.

## References

1. Freebase Data Dumps. 2013
2. KBpedia