toggle flipflop
T-flipflops are clocked flipflops with only one clock input.
The output states of a T- flipflop cannot be fixed, only the change of the output states. This occurs at each edge change of the clock pulse. Since the output state of the T-flipflop changes twice per clock frequency, the flipflop is also used as a frequency divider.
A T-flipflop can also be formed from a JK-flipflop if both inputs are set to HI- level.