As opposed to most other EPROM emulators, the design discussed in this article provides a virtually perfect imitation of a ‘real-life’ 27C256 device, which may be programmed in any programmer as well as inserted into the target system.An EPROM emulator is a useful if not indispensable tool if you are into developing software for a system employing an EPROM for storage of executable code or fixed data. Such a ‘programmable imitation EPROM’ obviates the need to erase an EPROM after any programming cycle, before the new (and hopefully improved) program may be loaded into the chip. Erasing an EPROM with the aid of UV light usually takes about 20 minutes, which, many of you will agree, is an annoyingly long time.