EPROM stands for Erasable Programmable Memory. It is a type of chip that can hold data significantly longer than other types of ROM chips. EPROM can be programmed a number of times in contrast with PROM (Programmable Read Only Memory), which can be programmed only once.
The physical structure of an EPROM consists of several components. This chip is made up of rows and columns. Each intersection made by the rows and columns is called a cell. Every cell has its own control gate transistor and floating gate transistor. A layer of fine oxide separates the said types of transistors.
A grid row, also known as the wordline, is connected to the floating gate. The value of the cell is 1 if the connection of the floating gate to the wordline exists. On the other hand, the value of the cell is 0 if the connection between the floating gate transistor and wordline is removed.
EPROM uses a number of technologies for its features. It is configured and/or re-configured using a specific tool aptly known as an EPROM programmer. Configuring an EPROM involves changing the values of a number of cells from 1 to 0 through a process called tunneling. Tunneling is done by allowing electricity to pass through the control gate and floating gate to remove the link between the latter with the wordline.
To erase the EPROM programming, a device called an EPROM Eraser is used. The EPROM chip is placed under the EPROM Eraser which directs ultraviolet light to the EPROM chip. The energy of the ultraviolet light will unblock all the cells of the chip, subsequently changing all the values of the EPROM cells into 1.