![]() That means, the clock signal transitions either from Logic Low to Logic High or Logic High to Logic Low.įollowing are the two types of edge triggering based on the transitions of clock signal. There are two types of transitions that occur in clock signal. It is highlighted in the following figure. If the sequential circuit is operated with the clock signal when it is in Logic Low, then that type of triggering is known as Negative level triggering. If the sequential circuit is operated with the clock signal when it is in Logic High, then that type of triggering is known as Positive level triggering. Following are the two types of level triggering. There are two levels, namely logic High and logic Low in clock signal. Types of Triggeringįollowing are the two possible types of triggering that are used in sequential circuits. So, the frequency at which the sequential circuits can be operated accordingly the clock signal frequency has to be chosen. All sequential circuits are operated with clock signal. The reciprocal of the time period of clock signal is known as the frequency of the clock signal. ![]() ![]() In this case, the time period will be equal to sum of ON time and OFF time. This pattern repeats with some time period. This signal stays at logic High (5V) for some time and stays at logic Low (0V) for some other time. In the above figure, train of pulses is considered as clock signal. This clock signal is shown in the following figure. We can represent the clock signal as train of pulses, when ON time and OFF time are not same. In this case, the time period will be equal to either twice of ON time or twice of OFF time. This signal stays at logic High (5V) for some time and stays at logic Low (0V) for equal amount of time. N the above figure, square wave is considered as clock signal. We can represent the clock signal as a square wave, when both its ON time and OFF time are same. Clock signalĬlock signal is a periodic signal and its ON time and OFF time need not be the same. In this section, let us discuss about the clock signal and types of triggering one by one. Therefore, the outputs of synchronous sequential circuits are in synchronous with either only positive edges or only negative edges of clock signal. That means, all the outputs of synchronous sequential circuits change (affect) at the same time. If all the outputs of a sequential circuit change (affect) with respect to active transition of clock signal, then that sequential circuit is called as Synchronous sequential circuit. ![]() Therefore, most of the outputs of asynchronous sequential circuits are not in synchronous with either only positive edges or only negative edges of clock signal. That means, all the outputs of asynchronous sequential circuits do not change (affect) at the same time. If some or all the outputs of a sequential circuit do not change (affect) with respect to active transition of clock signal, then that sequential circuit is called as Asynchronous sequential circuit. Outputs depend on both present inputs and present state.įollowing are the two types of sequential circuits − ![]() Some sequential circuits may not contain combinational circuits, but only memory elements.įollowing table shows the differences between combinational circuits and sequential circuits. Therefore, sequential circuits contain combinational circuits along with memory (storage) elements. Previous output is nothing but the present state. The output(s) of sequential circuit depends not only on the combination of present inputs but also on the previous output(s). This sequential circuit contains a set of inputs and output(s). The following figure shows the block diagram of sequential circuit. All these circuits have a set of output(s), which depends only on the combination of present inputs. We discussed various combinational circuits in earlier chapters. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |