Shift registers are a type of sequential logic circuit, mainly for storage of di

Question

Shift registers are a type of sequential logic circuit, mainly for storage of digital data. They are a group of flip-flops connected in a chain so that the output from one flip-flop becomes the input of the next flip-flop. Most of the registers possess no characteristic internal sequence of states. Basic types of shift registers include Serial In–Serial Out, Serial In–Parallel Out, Parallel In–Serial Out, Parallel In–Parallel Out, and bidirectional shift registers.

A register that goes through a prescribed sequence of states upon the application of input pulses is called a counter. The input pulses may be clock pulses, or they may originate from some external source and may occur at a fixed interval of time or at random. Counter circuits are used in digital systems for many purposes. They may count the number of occurrences of certain events, generating timing intervals for control of various tasks in a system; keep track of time elapsed between specific events, and so on.

Please TYPE the answeres for the following:

• What is the principle of operation of a bidirectional shift register? Describe one practical application of bidirectional shift register.
• What is the principle of operation of an Asynchronous Counter? Describe one practical application of Asynchronous Counter.

Explanation / Answer

If we want to shift the data in which we are working on left or right we should probably use the bidirectional shift register. Basic , universal and derived gates or MUX can be used to enables the transfer of a data bit from the right to left or to the left from right, depending on the level of a control line.

When a bit is input on the right, all the bits move one place to the left, and the leftmost bit disappears.

Bilateral Shift registers are commonly used in converters that translate parallel data to serial data and this parallel data can also be used to convert it into the serial data.

Shift registers can also be used as delay circuits and digital pulse extenders to extend the pulse signal

A asynchronous counter is a setup where the external clock is connected to the clock input of the first flip. So, the first most flip flop changes state at the falling edge of each clock pulse, but the second flipflop changes only when triggered by the falling edge of the Q output of the first flip flop.

Clock Signal have basicaaly no use in Asynchronous counters because they are those whose output is free from the clock signal. Because the flip flops in asynchronous counters are supplied with different clock signals, there may be delay in producing output.

Due to its independency from clock signal it doesn't have wide applications as the results of previous input and the clock signal is necessary to save the information to the memory or for the continuation of the loop.

The required number of logic gates to design asynchronous counters is very less. So they are simple in design. Another name for Asynchronous counters is “Ripple counters”.

Asynchronous counters are not used widely because they impose the timing contraints as they are free from clock pulse on the remaining circuit.

It can be used in applications where we require the signals irrespective of the time.

D flip flops are basicaly use to design Asynchronous Counters.

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