Definitions for Digital Systems

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

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