EPROM

EPROMs date back to the 1970's and are among the first programmable memory devices.

Due to the technology used, the non-programmed cells of these memory devices have the logical state of "1". By programming it, the cell is converted to the logical state of "0". Erasing, or returning the cell to the state of 1 is possible with an ultraviolet light source. The light shines through a "window" right onto the chip. Specialized UV lamps for this purpose are available from specialized retailers.

Please Note: dirt on the window may cause problems when deleting. Transparent plastic foils or normal glass also hinder the reliable deletion of the memory.

As the window required for deleting is a considerable cost factor, almost all EPROM types are also available as OTP versions. These may be recognized by the absence of that window.

To protect the programmed data, the window can be covered by an opaque sticker after programming. Special stickers made of aluminum foil or stickers with one metallic side are well suited for that purpose.