ISRO 2008- ECE PROM

Question

A programmable device (PROM) is

(a) programmable OR and fixed AND array

(b) programmable AND and fixed OR array

(c) programmable AND and programmable OR array
(d) none

Answer 1

	PROM	PAL	PLA
Definition	Programmable ROM	Programmable Array Logic	Programmable Logic Array
AND array	Fixed	Programmable	Programmable
OR array	Programmable	Fixed	Programmable
Number of Minterms	All minterms are created. According to function OR is programmed	Simple implementation Not flexible For each OR gate same minterm should be implemented  separately	Only needed minterms are created using AND array. One minterm can be shared among all OR gates. Negation of minterms are done in OR array using EXOR gates.

So answer is A

Answer 2

(b)  programmable AND and fixed OR array

 

seems correct answer!