Digital Electronics/Circuits Multiple Choice Questions on “Shift Registers”.
1. Based on how binary information is entered or shifted out, shift registers are classified into _______ categories.
A. 2
B. 3
C. 4
D. 5
Answer: C
Clarification: The registers in which data can be shifted serially or parallelly are known as shift registers. Based on how binary information is entered or shifted out, shift registers are classified into 4 categories, viz., Serial-In/Serial-Out(SISO), Serial-In/Parallel-Out (SIPO), Parallel-In/Serial-Out (PISO), Parallel-In/Parallel-Out (PIPO).
2. The full form of SIPO is ___________
A. Serial-in Parallel-out
B. Parallel-in Serial-out
C. Serial-in Serial-out
D. Serial-In Peripheral-Out
Answer: A
Clarification: SIPO is always known as Serial-in Parallel-out.
3. A shift register that will accept a parallel input or a bidirectional serial load and internal shift features is called as?
A. Tristate
B. End around
C. Universal
D. Conversion
Answer: C
Clarification: A shift register can shift it’s data either left or right. The universal shift register is capable of shifting data left, right and parallel load capabilities.
4. How can parallel data be taken out of a shift register simultaneously?
A. Use the Q output of the first FF
B. Use the Q output of the last FF
C. Tie all of the Q outputs together
D. Use the Q output of each FF
Answer: D
Clarification: Because no other flip-flops are connected with the output Q, therefore one can use the Q out of each FF to take out parallel data.
5. What is meant by the parallel load of a shift register?
A. All FFs are preset with data
B. Each FF is loaded with data, one at a time
C. Parallel shifting of data
D. All FFs are set with data
Answer: A
Clarification: At Preset condition, outputs of flip-flops will be 1. Preset = 1 means Q = 1, thus input is definitely 1.
6. The group of bits 11001 is serially shifted (right-most bit first) into a 5-bit parallel output shift register with an initial state 01110. After three clock pulses, the register contains ________
A. 01110
B. 00001
C. 00101
D. 00110
Answer: C
Clarification: LSB bit is inverted and feed back to MSB:
01110->initial
10111->first clock pulse
01011->second
00101->third.
7. Assume that a 4-bit serial in/serial out shift register is initially clear. We wish to store the nibble 1100. What will be the 4-bit pattern after the second clock pulse? (Right-most bit first)
A. 1100
B. 0011
C. 0000
D. 1111
Answer: C
Clarification: In Serial-In/Serial-Out shift register, data will be shifted one at a time with every clock pulse. Therefore,
Wait | Store
1100 | 0000
110 | 0000 1st clock
11 | 0000 2nd clock.
8. A serial in/parallel out, 4-bit shift register initially contains all 1s. The data nibble 0111 is waiting to enter. After four clock pulses, the register contains ________
A. 0000
B. 1111
C. 0111
D. 1000
Answer: C
Clarification: In Serial-In/Parallel-Out shift register, data will be shifted all at a time with every clock pulse. Therefore,
Wait | Store
0111 | 0000
011 | 1000 1st clk
01 | 1100 2nd clk
0 | 1110 3rd clk
X | 1111 4th clk.
9. With a 200 kHz clock frequency, eight bits can be serially entered into a shift register in ________
A. 4 μs
B. 40 μs
C. 400 μs
D. 40 ms