I.1 What are GALs?

GALs (Generic Array Logic) are programmable logic devices. By appropriate
programming by the user, many standard gate functions can be resolved
into a single GAL chip.

Assuming you need the following logic functions for your circuit:

 - AND -Gate with 2 inputs
 - OR  -Gate with 2 inputs
 - NAND-Gate with 2 inputs
 - NOR -Gate with 2 inputs


Normally you would need FOUR standard TTL-ICs. These functions can be
replaced with ONE GAL. The main use of GALs is to make digital circuits as
simple as possible, by replacing many standard logic ICs by one or more
GALs.
A GAL is able, with appropriate programming, to replace all the logic
functions, such as for example: AND, OR, XOR, NAND, NOR, inverters,
FlipFlops, decoders (especially address decoders), mutiplexers, counters.
On top of all the GAL is reprogrammable (at least 100 times), so that the
desired logic functions may easily be altered.