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The Erasable Programmable Read Only Memory (EPROM) memory chip keeps all data even if the power is switched off. Because this type of memory is non-volatile, information is kept even after the power is switched off. An electrical gadget independently programs each EPROM. This programmable, reusable computer chip can then be entirely erased with a strong UV laser before reprogramming with a PROM programmer or PROM burner. The top of the package of an EPROM features a transparent fused quartz window that permits exposure to UV light. It is possible to see the silicon chip through this window.
Operation of EPROM
A single field effect transistor serves as a storage site. This field effect transistor has a channel. This channel has connections to the source and drains at each of its ends. An insulating oxide layer and a conductive gas electrode are applied to the channel’s surface. The following is additional oxide and a control gate electrode.
Data can be retrieved from the EPROM by decoding the address at the address pins and connecting it to the output buffers. The EPROM programming process cannot be undone electrically. UV light ionises the oxide, causing the stored charge to evaporate and the memory to be wiped at the same time.
Applications of EPROM
Since manufacturers can now modify the data in programmable read-only memory before selling a device, EPROM is frequently used in personal computers.
It was thought that because EPROM was too expensive for mass manufacture, it would only be used for development. However, it was found that EPROM was more affordable for low-scale manufacturing.
Some microcontrollers employed on-chip EPROM, such as the Intel 8048, the Freescale 68HC11, the PIC microcontroller (C version), etc. Windowed versions of these microcontrollers were available, mostly employed for writing and maintaining programs.
Advantages of EPROM
These are a few advantages of EPROM:
- EPROM maintains its memory even when the power is out since it is non-volatile. Thus, the requirement of RAM is low
- The EPROM has a small but significant amount of erase cycles
- Since an EPROM is Reprogrammable, its data can be erased and changed
Disadvantages of EPROM
The following list includes certain EPROM drawbacks:
- EPROM transistors have higher resistance
- The data on the EPROM must be erased using UV light. Electrical signals cannot be used to do this
- In EPROM, a specific byte of data cannot be erased. The entire data set is removed
- EPROM has a high static power requirement
- The data in EPROM must be deleted over some time. In contrast to EEPROM, where data may be instantly erased, this cannot be done
Selection Criteria
When selecting EPROM chips, consideration must be given to various performance factors and the choice of a serial or parallel data bus.
- Operating current is the absolute minimum current necessary for active chip operation
- Standby current is the minimal minimum current needed when doing nothing
- The term “power dissipation,” often expressed in watts or milliwatts, refers to the total amount of power the device uses
- Access time is a cycle that begins when the CPU sends a request to memory and ends when the CPU receives the requested data. It is measured in nanoseconds (ns)
