| 摘要 |
A programmable logic device (PLD) includes a fixed EXCLUSIVE OR gate and a programmable logic array (PLA). The PLA includes a plurality of AND gate and a plurality of OR gates, the output of each AND gate being programmably connected to an input of each of the plurality of OR gates. The output of one of the OR gates of the PLA array is fed to one of the inputs of the fixed EXCLUSIVE OR. Since the output of each of the AND gates is available to each of the OR gates in the PLA array, implementation of the EXCLUSIVE OR function is facilitated and the number of product terms (AND gates) required is reduced as compared to known PLDs. The output of a programmable array logic (PAL) array having a plurality of AND gates non-programmably connected to an OR gate is connected to the other one of the inputs of the fixed EXCLUSIVE OR gate. Very wide EXCLUSIVE OR functions are readily implemented using a plurality of identical logic cells having the above architecture, each of which generate an intermediate result which is fed to a final logic cell implementing a wide EXCLUSIVE OR of the intermediate results.
|
