PROM programmer

7-90 elektor July/august 1980 Programmable Read Only Memories 1 are finding their way into more and more electronic construction projects. Unfortunately, programming equip- ment (and services) tend to be rather expensive as far as the amateur constructor is concerned. It is also possible that the stringent program- ming requirements of most PROMs can act as a deterrent to the would-be programmer designer. For these reasons we have decided to include here a circuit which can be used to program one of the smaller and more common types of PROM. The device in question is the 82S23 which is organised as a 32 x 8 bit memory. (The 82S123 can also be programmed — this has tri-state outputs whereas the 82S23 has open- 2 collector outputs). 1 cycle 5 67 The signals generated by the programmer conform to the manufacturer"s specifications. These are shown in figure 1. The Vcc signal is the supply voltage for the PROM -Start and CE is the signal which has to be .000 00 applied to the "chip e...