Erasible Programmable Read-Only Memory  or EPROM, is a computer memory chip that retains data even after a power failure - that is, non-volatile (non-volatile). It is a set of floating-gate transistors that are programmed separately by an electronic device that provides higher voltage than is commonly used in electronic circuits. Once the program is complete, the EPROM can only be erased by intense ultraviolet radiation.

Specifically, ROMs are generally used for small fixed storage purposes, such as game cards, general electronic product programs are stored in ROM, but EPROM storage is needed for less frequent changes, such as BIOS programs on computers, which are often rewritten in RAM (read-access momery readable and write memory), such as memory.

Structure of cascade gate injection MOS tube. When the floating grid Gf is not charged, the normal logical high level added to the control grid Gc can make the MOS tube conductive. When a negative charge is charged on the floating grid, a normal logical high level is added to the control grid and the MOS tube is not conductive, which is equivalent to not having this storage element connected. Programming uses a high voltage between the drain and the source to generate avalanche breakdown, while adding a high voltage pulse to the control grid, some energetic electrons pass through the SiO2 layer to the floating grid, forming a charge charge charge.

When erasing is required, the transparent window on the EPROM surface can be exposed to a certain intensity of ultraviolet light, and the charge on the floating grid can be leaked after 15-20 minutes. Usually, the transparent window should be closed and shaded to ensure that the charge on the floating grid is stored for a long time. This EPROM erased with ultraviolet light is also called UVEPROM.

In addition, there is an EPROM that is erased by the voltage signal, also known as EEPROM (or EPROM). The stacked MOS tube is also used in its storage unit, and the reverse high voltage pulse is applied on the control grid when erasing.

Because data in EPROM can be modified, it is particularly suitable for making read-only memory in which data needs to be modified.