Two Marks Questions with Answers

Two Marks Questions with Answers

Q.1 Define PLD.

Ans. : Programmable Logic Devices consist of a large array of AND gates and OR gates that can be programmed to achieve specific logic functions.

Q.2 Give the classification of PLDs.

Ans. : PLDs are classified as :

• PROM (Programmable Read Only Memory),

• Programmable Logic Array (PLA),

• Programmable Array Logic (PAL), and

• Generic Array Logic (GAL)

Q.3 What is a PLA?

Ans. : PLA stands for Programmable Logic Array, which is a LSI component. In PLA, both AND and OR gates have fuses at the inputs, therefore in PLA both AND and OR gates are programmable. The outputs from OR gates go through fuses as inputs to output inverters so that final output can be programmed as either AND-OR or AND-OR-INVERT.

Q.4 Whether PAL is same as PLA ? Explain.

(Refer sections 9.4 and 9.5)

Q.5 What is the advantage of PLA over ROM ?

(Refer section 9.5)

Q.6 How does the architecture of a PLA different from a PROM ?

(Refer section 9.5)

Q.7 Why was PAL developed ?

Ans. : PAL is a PLD that was developed to overcome certain disadvantages of PLA, such as longer delays due to additional fusible links that result from using two programmable arrays and more circuit complexity.

Q.8 Why the input variables to a PAL are buffered ?

Ans. : The input variables to a PAL are buffered to prevent loading by the large number of AND gate inputs to which available or its complement can be connected.

Q.9 Draw the block diagram of PLA.

(Refer Fig. 9.3.1)

Q.10 What is PROM ?

Ans. : PROM stands for programmable read only memory. It has fixed AND array and programmable OR array. It can be used to implement boolean functions in standard SOP form.

Q.11 State the difference between PROM, PLA and

PAL. (Refer Table 9.5.1)

Q.12 What happens to the information stored in a memory location after it has been read and write operation ?

Q.13 Define modularity.

Q.14 Outline about PLA.

(Refer section 9.3)