Question 9.10: Suppose that you observe the output waveforms (green) that a...
Suppose that you observe the output waveforms (green) that are indicated for the counter in Figure 9–59. Determine if there is a problem with the counter.
The Q_{2} waveform is incorrect. The correct waveform is shown as a red dashed line.
You can see that the Q_{2} waveform looks exactly like the Q_{1} waveform, so whatever is causing FF1 to toggle appears to also be controlling FF2.
Checking the J and K inputs to FF2, you find a waveform that looks like Q_{0}. This result indicates that Q_{0} is somehow getting through the AND gate. The only way this can happen is if the Q_{1} input to the AND gate is always HIGH. However, you have seen that Q_{1} has a correct waveform. This observation leads to the conclusion that the lower input to the AND gate must be internally open and acting as a HIGH. Replace the AND gate and retest the circuit.