This universal device programmer supports a wide range of PROMs, which are the oldest version of programmable read-only memory (PROM) and uses technology called "bipolar". Because of its old technology, bipolar PROMs require a variety of high voltages for programming and therefore PROMs are not supportable by lower cost programmers. Bipolar PROMs are programmable only once and cannot be erased.

CMOS PROMs

After bipolar, the next major technology that emerged was CMOS (Complementary metal oxide silicon). CMOS allows the design of UV-erasable cells which gave rise to erasable PROMs or EPROMs. Memories chips that are based on the EPROM cells can be erased and reprogrammed numerous times -- provided that the IC chips have a glass (actually quartz) windows to allow UV lights to go through. Those do not have glass windows cannot be erased and therefore are called one-time-programmable, or OTP, EPROMs.

While all EPROMs are byte-wide (8-bit) or word-wide (16-bit), most PROMs are only 4-bit or 8-bit wide.

Since PROMs are very old memory devices, it is not always possible to find them these days. Therefore it helps to know which ones are compatible, in case the original part number you need is not available.

For the same reason, it is also important to buy a programmer that supports a wide variety of bipolar PROMs.