Computer Science Principles V11

Clive W. Humphris

COUNTING: Bistable or Flip Flop.  

The logic circuits in this module make practical use of the positive and zero rails to apply the logic levels to the gates. Remember logic can be represented as HIGH or LOW, 1 or 0, ON or OFF, 5V or 0V, they can all be interchanged.

R1 and R2 form pull-up resistors, meaning that if the switch S1 position is open circuit the input to the logic gate will be pulled up to the supply rail.

There is negligible input current and so the voltage dropped across the resistor will be small and can be ignored.

The bi-stable as its name implies has two stable states. Place S1 in one position and the output on Q is HIGH and in the other it's LOW. NOT Q will always take up the opposite logic state.

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