The transition from Logic High to Logic low occurs in the clock signal of negative edge triggering. The diagram of positive edge triggering is given below. So, in positive edge triggering, the circuit is operated with such type of clock signal. The transition from Logic Low to Logic High occurs in the clock signal of positive edge triggering. In clock signal of edge triggering, two types of transitions occur, i.e., transition either from Logic Low to Logic High or Logic High to Logic Low.īased on the transitions of the clock signal, there are the following types of edge triggering: Positive edge triggering Below is the diagram of Negative level triggering: Edge triggering So, in this triggering, the circuit is operated with such type of clock signal. In negative level triggering, the signal with Logic Low occurs. Below is the diagram of positive level triggering: Negative level triggering In a positive level triggering, the signal with Logic High occurs. There are the following types of level triggering: Positive level triggering In level triggering, when the clock pulse is at a particular level, only then the circuit is activated. The logic High and logic Low are the two levels in the clock signal. These are two types of triggering in sequential circuits: Level triggering It repeats with a certain time period, which will be equal to twice the 'ON time' or 'OFF time'. Sometimes, the signal stays at logic, either high 5V or low 0V, to an equal amount of time. Below is a diagram which represents the clock signal:Ī clock signal is considered as the square wave. When ON time and OFF time of the clock signal are the same, a square wave is used to represent the clock signal. Clock Signal and Triggering Clock signalĪ clock signal is a periodic signal in which ON time and OFF time need not be the same. The synchronization of the outputs is done with either only negative edges of the clock signal or only positive edges. The output is stored in either flip-flops or latches(memory devices). In synchronous sequential circuits, synchronization of the memory element's state is done by the clock signal. The asynchronous sequential circuit is similar to the combinational circuits with feedback. The un-clocked flip-flops or time-delayed are the memory elements of asynchronous sequential circuits. The internal state is changed when the input variable is changed. The asynchronous circuits do not use clock pulses. So, the changes in the input can change the state of the circuit. The asynchronous circuit is operated through the pulses. The clock signals are not used by the Asynchronous sequential circuits. Types of Sequential Circuits Asynchronous sequential circuits It is not simple to design a sequential circuit. The combinational circuit is simple to design. The clock signal is required for sequential circuits. The clock signal is not required for combinational circuits. In the sequential circuit, memory elements play an important role and require. In combinational circuits, memory elements are not required. The feedback path is present in the sequential circuits. The feedback path is not present in the combinational circuit. The outputs of the sequential circuits depend on both present inputs and present state(previous output). The outputs of the combinational circuit depend only on the present inputs. So, the sequential circuit can contain only the memory element.ĭifference between the combinational circuits and sequential circuits are given below: A sequential circuit doesn't need to always contain a combinational circuit. So, the sequential circuit contains the combinational circuit and its memory storage elements. The previous output is treated as the present state. The outputs of the sequential circuits depend on both the combination of present inputs and previous outputs. The sequential circuit is a special type of circuit that has a series of inputs and outputs. Below is the block diagram of the synchronous logic circuit. The combinational circuits have set of outputs, which depends only on the present combination of inputs. In our previous sections, we learned about combinational circuit and their working.
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