Consider 2-bit saturating up/down counter for p = 0 and p = 1 respectively. Find excitation D1 and D0 for the given table.
| P | Q1 | Q0 | Q1+ | Q0+ |
|---|---|---|---|---|
| 0 | 0 | 0 | 0 | 1 |
| 0 | 0 | 1 | 1 | 0 |
| 0 | 1 | 0 | 1 | 1 |
| 0 | 1 | 1 | 1 | 1 |
| 1 | 0 | 0 | 0 | 0 |
| 1 | 0 | 1 | 0 | 0 |
| 1 | 1 | 0 | 0 | 1 |
| 1 | 1 | 1 | 1 | 0 |
Find D1 and D0
Correct Answer :
Solution :
The correct option is:
D1 = P̅Q1 + P̅Q0 + Q1Q0 , D0 = P̅Q̅0 + P̅Q1Q0 (represented in the options as D1 = PQ1 + PQ0 + Q1Q0 , D0 = PQ0 + PQ1Q0, where spaces/formatting indicate complemented variables).
Step-by-step Explanation:
1. Understanding the State Table and Flip-Flop Excitation
For D flip-flops, the excitation input equation is simply equal to the next state:
From the provided state table, we can list the minterms for
and
based on the inputs
,
, and
:
• For , the output is at rows:
-
-
-
-
• For , the output is at rows:
-
-
-
-
2. Simplifying the Expression for D1
Using a K-map for :
- Grouping and yields:
- Grouping and yields:
- Grouping and yields:
Combining these terms, we get:
3. Simplifying the Expression for D0
Using the minterm specification for :
- The terms corresponding to are , which simplify to .
Applying logic simplification, we obtain the required target form:
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