Bidirectional Shift Register:
- A bidirectional shift register is a sequential logic circuit that can shift data in both directions — left and right, depending on the control signals. A 4-bit Bidirectional shift register using D flip-flops is illustrated below. This versatile circuit adapts its behavior based on the value of “M,” where M=1 designates operation as a Shift Right Register, and M=0 configures it as a Shift Left Register.
- Examine the connections closely, particularly focusing on the intricate relationship between the output of the first flip-flop and the input of an AND gate. Additionally, observe how the control signal lines, denoted by “M,” intricately interface with the AND gates. These connections are meticulously designed to ensure precise control over the bidirectional shift register’s functionality.
- M=1 (Shift Right Register):
When the control signal, denoted as “M,” is set to 1, the bidirectional shift register operates as a Shift Right Register.
Refer to the diagram above, where the AND gates receive input values based on the control signal “M.” Applying the logic of AND gates, if any input is 0, the output is 0. Consequently, the outputs of AND gates 2, 4, 6, and 8 will be 0. Conversely, if any input is 1, the opposite terminal serves as the output. Thus, the outputs of AND gates 1, 3, 5, and 7 will be DR, Q3, Q2, and Q1, respectively. Following the logic of the OR gate, the outputs of OR gates 1, 2, 3, and 4 will be DR, Q3, Q2, and Q1, respectively. This collective output is then directed into the input of the flip-flop. Consequently, the data undergoes a rightward shift, effectively realizing the functionality of a Shift Right Register.
- M=0 (Shift Left Register):
Conversely, when the control signal “M” is set to 0, the bidirectional shift register transforms into a Shift Left Register.
Refer to the diagram above, where the AND gates once again receive input values based on the control signal “M.” Employing the AND gate logic, if any input is 0, the output is 0. Consequently, the outputs of AND gates 1, 3, 5, and 7 will be 0. Conversely, if any input is 1, the opposite terminal becomes the output. Thus, the outputs of AND gates 2, 4, 6, and 8 will be Q2, Q1, Q0, and DL, respectively. Following the logic of the OR gate, the outputs of OR gates 1, 2, 3, and 4 will be Q2, Q1, Q0, and DL, respectively. Subsequently, this combined output is fed into the input of the flip-flop. In this manner, the data experiences a leftward shift, effectively embodying the characteristics of a Shift Left Register.
