Page 203 - Bebop to The Boolean Boogie An Unconventional Guide to Electronics Fundamentals, Components, and Processes

This diagram indicates a
fusible link technology, because
all of the links are present
when the device is in its
unprogrammed state. Similarly,
the following examples are
based on fusible link devices
unless otherwise stated.

Programmable Array

Logic (PAL)
t t t Many applications do not
AND Array
W X Y require both the AND and OR
Figure 16-8. Generic structure of a PLA arrays to be programmable. In
(programmable AND, programmable OR) the case of programmable array
logic (PAL)s99 devices, only the
a AND array is programmable
T $ T Programmable Link while the OR array is predefined

(Figure 16-9).
Although PALs are less
flexible than PLAs, they
operate somewhat faster because
n
R‘ hard-wired connections take
CD
e less time to switch than their
0
m programmable equivalents. lo

8 In conversation, PAL is pronounced
as a single word to rhyme with
“gal.”
9 PAL is a registered trademark of
Monolithic Memories Inc.
10 There are also variations on PALs
Figure 16-9. Generic structure of a PAL called generic array logic (GAL)
(programmable AND, predefined OR) devices from Lattice Semiconductor
Corporation (www.1atticesemi.com).