:twisted:
The simple gates circuit for reseting the counter is not secure in all cases.
Try to figure out what happen if one or more counter bistables is faster than others. This bistables will go to 0 before others perform this step, and your gates detect a diferent than 60 combination so, because the gates are faster than counter, the reset signal will be cutt off before the entire counter is completely reset, and the counter will be not in 0 but in an random state.
To make the reset process secure enough, the reset signal must be susteined long enough to assure entire counter reset.
You can found several ways to make this.