Problem

Solutions For Digital Design Chapter 4 Problem 29P

Step-by-Step Solution

Solution 1

Refer to Table 4.8 in the textbook for the truth table of priority encoder.

Change the priority to the bit from bit.

Prepare a truth table for the priority encoder with the highest priority given to .

Picture 17

The Table 1 shows that the has the highest priority. W represents the valid condition. If one of the inputs is 1, then the valid (W) will be 1. If the valid (W) is 0, then outputs X and Y will have don’t care.

Draw the Karnaugh map for . Substitute 0 and 1, for the don’t care terms.

Picture 13

The expression for the output is,

Thus, the expression for the output is .

Draw the Karnaugh map for . Substitute 0 and 1, for the don’t care terms.

Picture 14

The expression for the output is,

Thus, the expression for the output is .

Draw the Karnaugh map for . Substitute 0 and 1, for the don’t care terms.

Picture 12

The expression for the output is,

Thus, the expression for the output is .

Draw the four-input priority encoder.

Picture 1

Therefore, four input priority encoder circuit has been implemented with input having the highest priority.

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