Programmable Read-Only Memory (PROM) is a type of permanent memory chip that can be programmed by the customer. Unlike a ROM chip, which is made during the manufacturing process of the chip, PROMs are programmed after being manufactured. PROMs are used for storage when their content is not expected to change. However, they have been largely replaced by reprogrammable EPROMs and EEPROMs in many applications.
How Does PROM Work?
The PROM chip is manufactured with a grid of fuses and anti-fuses. The user can selectively program the memory cells by blowing the fuses or creating anti-fuses. When a fuse is blown, the memory cell is programmed to a logic 1, and when an anti-fuse is created, the memory cell is programmed to a logic 0. Once a cell is programmed, it cannot be changed.
What Are the Advantages of PROM?
The main advantage of PROM is its permanency. Once a cell is programmed, it stays that way. This makes it ideal for storing firmware, boot code, and other critical information that should not be altered. PROM is also a low-cost solution since it does not require a power supply or any additional circuitry to maintain its data.
What Are the Disadvantages of PROM?
The biggest disadvantage of PROM is that it is not reprogrammable. Once a cell is programmed, it cannot be changed or erased. This means that if there is an error in the programming, the entire chip must be discarded and replaced with a new one. PROM also has a limited capacity and can only store a fixed amount of data.
Conclusion
PROM is a type of permanent memory chip that can be programmed by the customer. It has been largely replaced by reprogrammable EPROMs and EEPROMs in many applications. However, PROM is still used for storing firmware, boot code, and other critical information that should not be altered. The main advantage of PROM is its permanency, while the biggest disadvantage is that it is not reprogrammable.
FAQ
What is the difference between PROM and ROM?
ROM is a type of non-volatile memory that is programmed during the manufacturing process of the chip. PROM, on the other hand, is programmed by the customer after being manufactured.
What is the difference between PROM and EEPROM?
EEPROM is erasable and reprogrammable, while PROM is not. This means that the data stored in an EEPROM can be changed, while the data stored in a PROM cannot.
What is PROM used for?
PROM is used for storing firmware, boot code, and other critical information that should not be altered.
Final Thoughts
Programmable Read-Only Memory or PROM is a permanent memory chip that can be programmed by the customer. While it has been largely replaced by reprogrammable memory chips, it is still used for storing critical information that should not be altered. PROM is low-cost and does not require a power supply or additional circuitry, making it ideal for many applications.
