This set of Logic Design Multiple Choice Questions & Answers (MCQs) focuses on “VHDL Operators – Set 2”.

1. VHDL has 3 shift operators.

a) True

b) False

View Answer

Explanation: VHDL has 6 Shift operators:

sll – shift left logical, filled with ‘0’

srl – shift right logical, filled with ‘0’

sla – shift left arithmetic, filled with rightmost bit

sra – shift right arithmetic, filled with leftmost bit

rol – rotate left

ror – rotate right

Hence the answer is false.

2. VHDL Shift operators can be used only on bit_vector data types.

a) True

b) False

View Answer

Explanation: The shift operators are used to shift or rotate a bit_vector.

Hence the answer is True. The VHDL shift operators won’t work on other data types.

3. A is an 8-bit vector equal to “10010101”. Perform A sll 1.

a) 00101010

b) 10010100

c) 10010000

d) 00010000

View Answer

Explanation: The operator sll performs shift left logical operation, remaining bits are filled with ‘0’. A is shifted logically to the left by one bit, remaining bits are filled with zeros. Thus, on shifting A to the left by 1 bit, we get the result as 00101010.

4. A is an 8-bit vector equal to “10010101”. Perform A srl 1.

a) 01001010

b) 00100101

c) 10010000

d) 00010000

View Answer

Explanation: The operator srl performs shift right logical operation, remaining bits are filled with ‘0’. A is shifted logically to the right by one bit, remaining bits are filled with zeros. Thus, on shifting A to the right by 1 bit, we get the result as 01001010.

5. A is a 7-bit vector equal to “1001101”. Perform A sla 3.

a) 1101111

b) 1101000

c) 1100000

d) 1111111

View Answer

Explanation: The operator sla performs shift left arithmetic, remaining bits are filled with the rightmost bit. A is shifted arithmetically to the left by 3 bits, remaining bits are filled with the rightmost bit.

6. A is an 8 bit vector equal to “10010101”. Perform A sra 1.

a) 11001010

b) 00100101

c) 10010000

d) 00010000

View Answer

Explanation: The operator sra performs shift right arithmetic, remaining bits are filled with the leftmost bit. A is shifted arithmetically to the right by 1 bit, remaining bits are filled with the leftmost bit.

7. A is an 8 bit vector equal to “10010101”. Perform A rol 1.

a) 00101011

b) 00100101

c) 10010000

d) 00010000

View Answer

Explanation: The operator rol performs rotate left operation. A is rotated to the left by 1 bit. Thus, on rotating A to the left by 1 bit, we get the result as 00101011.

8. A is an 8 bit vector equal to “10010101”. Perform A ror 1.

a) 11001010

b) 00100101

c) 10010000

d) 00010000

View Answer

Explanation: The operator ror performs rotate right operation. A is rotated to the right by 1 bit. Thus, on rotating A to the right by 1 bit, we get the result as 11001010.

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