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EPROM – Erasable Programmable Read-Only Memory Overview

EPROM (Erasable Programmable Read-Only Memory) was quite popular during its heyday, particularly in the 1980s and 1990s. It played a significant role in early computing and digital electronics. In this article, we will discuss what is EPROM, its characteristics, functions, applications, advantages, disadvantages and how it differs from EEPROM.


Definition of Erasable Programmable Read-Only Memory

EPROM stands for Erasable Programmable Read-Only Memory. It is a type of non-volatile memory that can be programmed and erased using UV rays. EPROMs are widely used in the field of electronics and computing for storing small amounts of data that need to be retained even when the power is turned off. However, what distinguishes EPROM from other types of ROM is its erasability. EPROMs can be erased by exposing them to ultraviolet (UV) light for a specified duration. The UV light removes the charge trapped in the floating-gate transistors, resetting the cells to their unprogrammed state. Once erased, EPROMs can be reprogrammed with new data.

Erasable Programmable Read Only Memory

Erasable Programmable Read-Only Memory chips consist of a grid of memory cells, each capable of storing a single bit of data. Each cell is composed of a floating-gate transistor that can be electrically programmed to store a charge, representing either a “0” or a “1.” The data in an EPROM chip is typically programmed at the manufacturer’s facility using specialized equipment.

EPROMs have been widely used in the past for firmware storage, microcontroller programming, and data storage in various electronic devices. However, they have largely been replaced by other non-volatile memory technologies such as Electrically Erasable Programmable Read-Only Memory (EEPROM) and Flash memory, which offer faster erasure and reprogramming times, higher storage densities, and lower power consumption.

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Rise and Fall of EPROM

Lets separate it to two parts for better understanding.

The Rise of EPROM


The 1970s and 1980s saw the rise of microprocessors and the need for a reliable and non-volatile memory for storing firmware and BIOS data. Before EPROMs, most memory was volatile, meaning it would lose its data once the power was turned off. The ability to store data without power was a significant advantage of EPROMs, making them ideal for various applications. EPROMs filled this need perfectly, as they allowed for the storage of fixed data that could be read by the microprocessor during boot-up.

Although EPROMs were not as flexible as modern flash memory, they could still be erased and reprogrammed multiple times, which was a significant advantage compared to regular ROMs. EPROMs were commonly used in early personal computers, gaming consoles, arcade machines, and other electronic devices that required firmware or BIOS storage.

The Fall of EPROM

Flash Memory

As technology progressed, flash memory emerged as a more convenient and efficient alternative to EPROMs. Flash memory allowed for easier and faster erasure and reprogramming without the need for UV light. With the rise of flash memory in the late 1990s and early 2000s, EPROMs gradually lost popularity. Flash memory offered higher densities, faster access times, and non-volatile storage, making it a more attractive option for modern electronic devices.

Characteristics of Erasable Programmable Read-Only Memory

  • All the programs in the EPROM are programmed by electronic device.
  • In EPROM, the data can be stored minimum up to 10-20 years.
  • In order to avoid unwanted exposure to UV light, the erasing window is kept covered to avoid accidental data loss.

Functions of Erasable Programmable Read-Only Memory

In EPROM, each storage location consists of a single field-effect transistor and each of them consists of a channel in the semiconductor body of the device. In order to get the data from the EPROM, the address pins of the EPROM is decoded and used to connect one word i.e., 8-bit byte of storage to the output buffer amplifiers. Each bit of the word is 1 or 0 that depends on the storage transistor being switched on and off and conducting, non-conducting.

The process of programming are not reverse electrically. In order to erase the data stored in the array of transistors, ultraviolet light is required. Generally, the EPROM must be removed from equipment to be erased as it is not practical to build in a UV light to erase the parts in the circuit.

Applications of Erasable Programmable Read-Only Memory

The potential and historical applications of EPROMs are as follows:


1. Firmware Storage

EPROMs were commonly used to store firmware in early computing devices and microcontrollers. Firmware is a type of software that provides essential control and functionality to hardware devices, and EPROMs allowed manufacturers to store this firmware permanently.

2. BIOS (Basic Input/Output System)

EPROMs were widely used to store the BIOS in personal computers and early gaming consoles. The BIOS is responsible for booting the computer and initializing essential hardware components during startup.

3. Embedded Systems

EPROMs were used in various embedded systems, such as industrial controllers, automotive electronics, and consumer electronics, where a fixed set of data or code needed to be stored without the risk of losing it when the power was turned off.

4. Development and Prototyping

EPROMs were often used by hardware developers and engineers during the development and prototyping stages of electronic devices. The rewritable capability of EPROMs allowed them to be used for testing different firmware versions without needing to produce new chips for every iteration.

5. Data Storage for Legacy Systems

Some older systems that were designed before the widespread adoption of modern non-volatile memory technologies still rely on EPROMs for data storage. These legacy systems may be found in critical infrastructure, aerospace, or other specialized applications.

6. Retro Gaming

eprom怀旧游戏中扮演重要角色community. Older gaming consoles and arcade machines used EPROMs to store game code and data. Enthusiasts and collectors often use EPROM programmers to modify and preserve classic game data or to create reproduction cartridges.

7. Educational and Historical Purposes

EPROMs are still utilized in educational settings and electronics museums to teach about early computing and memory technologies. They help students and enthusiasts understand the historical evolution of memory storage in digital electronics.

Advantages of Erasable Programmable Read-Only Memory

Below are some of the advantages of EPROM:

  • It is known as non-volatile memory and hence it retains the memory even when the power is turned off.
  • It is quite effective.
  • The data in the EPROM is reprogrammable which means the data can be erased and reprogrammed.

Disadvantages of Erasable Programmable Read-Only Memory

  • High resistance transistors are used in EPROM.
  • UV Light is required to erase the data in the EPROM. This is not possible practically as UV light sources can not be placed everywhere in the places of EPROM.
  • One particular byte cannot be deleted in EPROM, the entire data has to be deleted.
  • High static power consumption.
  • In EPROM, it takes sometime to erase the data. This is slightly different from EEPROM where the data can be erased immediately.
  • User has to keep the backup as the entire data will be deleted.

What is EEPROM?

3 Serial EEPROM

It is a kind of memory which can be erased electrically and reused. It is a non-volatile memory. The information saved in this format is accessible readily anytime to read. With the help of embedded microcontrollers, it can store data in electrical devices. Thesmart cards, remote keyless entry systems, SIM cards and credit cards are few items that make use of them.

存储一个小quanti eepm有优势ty of information. Only few seconds are required to remove all the data. Electrical signals are required to erase the data. In order to delete a byte from EEPROM, a user need two-transistor structure which uses 5 volts of power. One of the major benefit of EEPROM is that it may be erased without having to be removed from the computer system.

Read more about EEPROM

Difference between EPROM and EEPROM

Below are some of the main differences between the EPROM and EEPROM-

In EPROM, ultraviolet light is used to delete the content. In EEPROM, the electrical signal is used to delete the content.
It includes rock crystal window at the top. This unit is entirely covered with sheathed in opaque plastic.
The relative size of the cell in EPROM is one. The relative size of the cell in the EEPROM is three.
EPROM is a version of PROM. EEPROM is a version of EPROM.
EPROM is the external programming. EEPROM is the external programming.
If EPROM memory is erased then it can be reprogrammed. EEPROM also can be reprogrammed after its erased.
The used transistor in EPROM uses 12.5 volt The used transistor in EEPROM uses 5 volt.
Here in EPROM, hot electron injection programming technique is used. Here in EEPROM, tunnel effect is used as programming technique.
To erase the contents in EPROM, it takes 15-20 minutes. To erase the contents in EEPROM, it takes 5 milli seconds of time.
EPROM chip has to be taken out from the computer circuit to erase and reprogram the computer’s BIOS. EEPROM chip can be erased and reprogrammed without removing it.

Read Also:Read Only Memory (ROM) – Working, Types, Applications, Advantages & DisadvantagesEEPROM – Full Form, Principle, Operations, Memory Organization
Chakrasthitha is a B.E (Medical Electronics) and has work experience in MatLab and Lab View Software as Design Engineer at BCS innovations and Manipal hospital as Biomedical Engineer. She is an author, editor and partner at Electricalfundablog.


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