What was the protocol for programming GAL devices?
My recollection is that they were programmed using parallel addressing and this page on TI's website would seem to confirm this.

Not all PALs are eraseable btw. AMD &amp; Lattice's PALCEs are electrically eraseable (the standard PALs were not). I don't know about TI's TIBPAL &amp; TICPALs I linked-to but the programming docs make no mention of erasing.