Combinational circuit

The output is determined by the combinations of one or more inputs

Sequential circuit

Output is dependent on:

·      The current input to the circuit;

·      The previous inputs to the circuit.

Synchronous

Changes in output do not occur immediately there is a change in input, but the next time there is a clock pulse

Asynchronous

The next stage is triggered by the completion of the previous stage without reference to a clock pulse

Triggering

Level triggering in which the changes occur when the level of the pulse is either at 0 or 1.

Edge triggering in which the change occurs as the clock pulse rises from 0 to 1(rising or positive edge) or from 1 to 0 (falling or negative edge).

Flip-Flop

Edge triggered devices are called flip-flops.

Latch

Level sensitive devices are often referred to as latches