Editing EPROM (section)

==Application==
For large volumes of parts (thousands of pieces or more), [[Read-only memory#Solid-state ROM|mask-programmed ROMs]] are the lowest cost devices to produce. However, these require many weeks lead time to make, since the artwork or design in an IC mask layer or photomask must be altered to store data on the ROMs. Initially, it was thought that the EPROM would be too expensive for mass production use and that it would be confined to development only. It was soon found that small-volume production was economical with EPROM parts, particularly when the advantage of rapid upgrades of firmware was considered.

Some [[microcontrollers]], from before the era of [[EEPROM]]s and [[flash memory]], use an on-chip EPROM to store their program. Such microcontrollers include some versions of the [[Intel 8048]], the [[Freescale 68HC11]], and the "C" versions of the [[PIC microcontroller]]. Like EPROM chips, such microcontrollers came in windowed (expensive) versions that were used for debugging and program development. The same chip came in (somewhat cheaper) opaque OTP packages for production.  Leaving the die of such a chip exposed to light can also change behavior in unexpected ways when moving from a windowed part used for development to a non-windowed part for production.