Correct Answer - Option 3 : PLA economizes on the number of min-terms to implement Boolean functions
Explanation:
1. ROM is made of an AND gates array and OR gates array.
2. AND array provides all the combinations of inputs, and OR array is used to select the necessary combinations.
Therefore, the AND array is always fixed and the OR array is programmable. Hence it is a combinational circuit.
PLA (Programmable Logic Array)
1. It is used for the implementation of various combinational circuits using a buffer, AND gate, an OR gate.
2. It is used for the synthesis of SOP and POS canonical forms,
Hence it economizes on the number of min-terms to implement Boolean functions.
So option (3) is true.
Major Differences between ROM and PLA:
1. In PLA both AND and OR arrays are configurable unlike in ROM, whereas only the OR gates array is configurable.
2. PLA has the capability to take ‘don’t care terms’ (Boolean overlaps) into account in which ROMs are incapable.
3. ROM has all the combinations of product terms, and therefore, considered as the most general-purpose combinational logic device in contrast to PLA, which doesn’t have all the combinations.
