D Flip Flop The flip flop is a basic building block of sequential 4 bit ripple counter using flip flop circuits. It is a circuit that has two stable states and can store one bit of state information. The output changes state by signals applied to one or more control inputs.
Simulate The clock input is usually drawn with a triangular input. This flip-flop is a positive edge-triggered flip flop. Q0 is the previous state of Q and Q0 is the previous state of Q. PR and CLR are asynchronous inputs – that is the output responds to these input immediately. Click on their respective green switches and observe.
PR presets the output to 1 and CLR clears the output to 0. Both PR and CLR cannot be low at the same time – the output is undefined. Q follows D on the rising edge of CLK only when both PR and CLR are high. By setting both PR and CLR to high, it is identical to a basic D Flip Flop without these 2 control signals. FAQ Q output is now 0. What are the two ways the Q output can be changed to 1? CLK has a rising clock edge.