Differentiate between PLA and PAL. Explain 4-bit magnitude comparator

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Suresh Chand · Accepted Answer

The difference between PLA and PAL is given below BASIS PLA PAL Stands for Programmable Logic Array Programmable Array Logic Construction Programmable array of AND and OR gates. Programmable array of AND gates and fixed array of OR gates. Availability Less prolific More readily available Flexibility Provides more programming flexibility. Offers less flexibility, but more likely used. Cost Expensive Intermediate cost Number of functions Large number of functions can be implemented. Provides the limited number of functions. Speed Slow High A comparator used to compare two binary numbers each of four bits is called a 4-bit magnitude comparator. It consists of eight inputs each for two four bit numbers and three outputs to generate less than, equal to and greater than between two binary numbers. In a 4-bit comparator the condition of A>B can be possible in the following four cases: If A3 = 1 and B3 = 0 If A3 = B3 and A2 = 1 and B2 = 0 If A3 = B3, A2 = B2 and A1 = 1 and B1 = 0 If A3 = B3, A2 = B2, A1 = B1 and A0 = 1 and B0 = 0 Similarly the condition for A<B can be possible in the following four cases: If A3 = 0 and B3 = 1 If A3 = B3 and A2 = 0 and B2 = 1 If A3 = B3, A2 = B2 and A1 = 0 and B1 = 1 If A3 = B3, A2 = B2, A1 = B1 and A0 = 0 and B0 = 1 The condition of A=B is possible only when all the individual bits of one number exactly coincide with corresponding bits of another number. By using these Boolean expressions, we can implement a logic circuit for this comparator as given below:

Differentiate between PLA and PAL. Explain 4-bit magnitude comparator

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Differentiate between PLA and PAL. Explain 4-bit magnitude comparator

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