Introduction to Programmable Array Logic (PAL)

　　What is PAL?

　　PAL (Programmable Array Logic) is a low-density, one-time programmable logic device first introduced by MMI in the late 1970s. It is the first programmable logic device (PLD) with typical practical significance.

　　Components of PAL

　　The PAL device consists of three parts: a programmable AND logic array, a fixed OR logic array, and an output circuit. The PAL consists of a programmable "AND" plane and a fixed "OR" plane. The output of the OR gate can be selectively set to a registered state through a trigger. By programming the AND logic array, different forms of combinational logic functions can be obtained. In addition, in some models of PAL devices, a trigger and a feedback line from the trigger output to the AND logic array are set in the output circuit. This PAL device can also be used to easily construct various sequential logic circuits.

　　PAL Implementation Process

　　PAL devices are field programmable, and their implementation processes include anti-fuse technology, EPROM technology, and EEPROM technology. They are made using bipolar technology and fuse programming. PAL in EDA refers to a field programmable gate array logic device, and its internal circuit is improved on the basis of PLA.