The General Approach to Computing - A Ramble

You can, of course get sequential logic with a non-registered PAL. The 16L8 has feedback terms (the outputs can be fed back into the AND array), so you can make flip-flops. But I stand by what I said. Actually, registered PALs are easier than 16L8s in some cases. Firstly, you can tristate the outputs, force logic levels onto them and clock the device. For a _PAL_ (although not a GAL), the feedback is taken from the pins, so yuo can effectively force all the inputs to the AND array this way. And IIRC registered PALs (and GALs?) have a way to load the register for testing, and this is not disabled by the securioty fuse. Even without this, it should be possible to crack a PAL or GAL. The point is that any change in intenral state is noticeable at the pins. You can't have the device change state internally nad not see it (this is not true of more complex devices, of course). It's not trivial, though. -tony