A pin driver is an IC that takes controls to define what its output will be and sources or sinks current to make the appropriate voltage levels appear at the desired current. It's a complex circuit, but drives only one pin per channel. My old Data I/O UniSite has several (11?) pin driver boards capable of handling 7 or 8 channels per board.

A programmer needs a number of these pin drivers, generally one per pin, and it needs a way to route the signals to the programming socket pins in the appropriate order.

Yes, briefcase-size programmers, i.e, those that will fit in a briefcase, are cheaper and don't sacrifice the ability to program many devices that one is likely to want to handle today, but, what if you want to program a TMS2716? What about a 1702 (not likely, but ... ) or an MM5203? How about a 29MA16, or an early PIC or a Motorola MC68705P5?

I bought the UniSite because it was cheaper than all the adapters for my several briefcase programmers. Moreover, since I bought the UniSite on eBay, it cost less than any one of the adapters for my briefcase programmers, yet is the only programmer certified by each of the device manufacturers as capable of programming their devices. Further, I can be certain that it actually will program the parts in question, because it has the adapters with it, they are robust, and they actually work. I had the unfortunate experience with a XELTEK programmer that, while it claimed to handle a wide range of EEPROMS and PALs, it actually didn't. I had the same experience with another small programmer, in each case, costing on the order of $1kUS. I bought adapters and found that they were so fragile that one didn't dare put them in the briefcase, and, in several cases, particularly PLCC-packaged MACH-series AMD PLD's, they really didn't handle them properly, hence, destroyed a number of them. Those were, at the time, not inexpensive components.

Considering the time loss, expense, (I occasionally had to rent a programmer) and aggravation caused by the briefcase programmers (the manufacturers of which lacked the foresight to hire English-speaking employees for customer service) and the adapters, the full-price UniSite would have been a bargain.

If the O/P wants to program the old 27xxx-series EPROMS, all that's required is a debounced switch for Vpp, capable of sourcing up to 50 mA at up to 25 volts and logic-level controls to manage the programming process. His MCU can handle the timing and controls, though TTL buffers might be advisable. AFAIK, the datasheet for each of the 27xxx-series EPROMS thoroughly describes how to program the device.

RE