Microsoft Word - Digital Logic Design v_4_6a

Programmable Logic Arrays (PLA)
PLAs are similar to PROMs with the added flexibility of programmable AND array connections.
PLAs are the most flexible of the Program Logic Devices since both the AND and OR array
connections are field programmable. The drawbacks of the PLA technology are that they have
the highest cost per unit and the longest propagation delays.

 PLA Example: Implement F(A 0 ,A 1 )= A 0 .A 1 +A 0 .A 1

PLAs allow both the AND and OR array connections to be programmed. The complete fuse

map shows both the AND and the OR fuses. There may be opportunities to share product

terms between the outputs to improve efficiency.

00 11

12 03

0

1

A 0 A^1 0 1

p2

p1

An ... A 0

p 0

p 1

p(2

n+1

-1)^

Factory set

Intact Fuse

n-bit input

Programmable AND array

connections (^) F 0 ... F m
Programmable OR array