programmable array logic

The term Programmable Array Logic (PAL) is used to describe a family of programmable logic device semiconductors used to implement logic functions in digital circuits introduced by Monolithic Memories, Inc. (MMI) in mid 1978.PAL devices consisted of a small PROM (programmable read-only memory) core and additional output logic used to implement particular desired logic functions with few components.Using specialized machines, PAL devices were "field-programmable". Each PAL device was "one-time programmable" (OTP), meaning that it could not be updated and reused after its initial programming. (MMI also offered a similar family called HAL, or "hard array logic", which were like PAL devices except that they were mask-programmed at the factory.)
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<hardware> (PAL) A family of fuse-programmable logic integrated circuits originally developed by MMI. Registered or combinatorial output functions are modelled in a sum of products form. Each output is a sum (logical or) of a fixed number of products (logical and) of the input signals. This structure is well suited for automatic generation of programming patterns by logic compilers.
PAL devices are programmed by blowing the fuses permanently using overvoltage.
Today, more complex devices based on the same original architecture are available (CPLD's for Complex PLD's) that incorporate the equivalent of several original PAL chips. PAL chips are, however, still popular due to their high speed.
Generic Array Logic devices are reprogrammable and contain more logic gates.
(1995-12-09)