Mumbai University > COMPS > Sem 3 > Digital Logic Design and Analysis

Marks: 10 M

Year: June 2014

A shift register which can shift the data in only one direction is called a unidirectional shift register. A shift register which can shift the data in both directions is called a bi-directional shift register. Applying the same logic, a shift register which can shift the data in both directions as well as load it parallel, then it is known as a universal shift register.

The shift register is capable of performing the following operation: 1. Parallel loading 2. Left shifting 3. Right shifting

• Logic Circuit:

• The above diagram shows the logic circuit of universal shift register and this register performs its all the 3 operation depending on the connection of mode control (M).
• The mode control input is connected to logic 1 for parallel loading operation whereas it is connected to 0 for serial shifting.

• With mode control pin connected to ground, the universal shift register acts as a bi-directional register.

  For serial left operation, the input is applied to the serial input which goes to AND gate-1shown in figure. Whereas for the shift right operation, the serial input is applied to Dinput.