Electronic – the difference between a GAL and a PAL


I was reading this article (unfortunately a lengthy Dutch discussion) talking about a GAL. I have come across the GAL device before, but never really understood what a Generic Array Logic is. I know what a PAL is and I am under the impression that they're closely related, how do they compare?

Best Answer

Had to pull out my Tocci book for this one. PAL chips had an array of fuses inside them. The fuses served as interconnect for number of logic gates. They were programmed by blowing the fuses. GAL chips used EEPROM arrays to store these connections rather than fuses. They were reprogrammable, but not the way we think about reprogrammable devices now. The lower limit on the number of times they could be programmed was around 100. Unlike the PAL chips, whose outputs were hard wired to the output of a logic gate, the GAL chips had programmable output logic. So had sequential logic devices as part of the package. Many GAL chips could serve as pin compatible replacements for PAL chips. Both of these technologies are all but obsolete with our present PLD technology.