How exactly do PAL chips get programmed?

If you have the original, working, chip, it's worth sticking it into a programmer that supports that chip and manufacturer and trying to read it. Some manufactuerers did not copy-protect their PALs. For example, all the PALs in the VAX 11/730 CPU are readable (for all they're the key to the design). All PALs in every PERQ I've seen (including the AGW3300) are readable. All PALs in the Torch XXX -- apart from those on the (3rd party?) 68020 kludgeboard -- are readable. But then again, most PALs on clone ISA boards are protected. If the original chip is a HAL, you are out of luck. HAL == Hard Array Logic, it's a mask-programmed equivalent to a PAL. I've never found one that can be read out, I suspect the circuitry simply isn't there. -tony