Bounce Free Switching Circuit Verify that the output is boun

Bounce Free Switching Circuit (Verify that the output is bounce free) - Pic Below

In many cases, input signals to logic systems are derived from mechanical switches. These are subject to switch-bounce which can cause trouble in sequential circuits. To eliminate the bounce, switches should be buffered by a table as shown below: Verify that the output of the above circuits is \'bounce-free\'.

Solution

With the switch in the position shown the upper gate\'s output will be a one, regardless of the value of the other input. That and the one created by the bottom pull-up resistor drives the lower NAND to a zero . . . which races around back into the other gate. If the switch moves between contacts, and is for a while suspended in the nether region between terminals, the latch maintains its state because of the looped back zero from the bottom gate.

The switch moves a rather long way between contacts. It may bounce around a bit, but will never bang all the way back to the other contact. Thus, the latch\'s output is guaranteed bounce-free.