Verilog Logic and Circuit Quiz

Which Verilog construct is best suited to model combinational logic like adders or multiplexers?

• always @(posedge clk)

• initial block

• assign statement

• always @(posedge reset)

In a 4-bit adder/subtractor circuit, the control input is XORed with each bit of operand B. What is the purpose of this operation?

• To detect carry propagation

• To enable signed number operations

• To convert addition into subtraction

• To avoid overflow

In a full subtractor, the borrow output depends on:

• Only A and B

• Only Bin and A

• A, B, and Bin

• A and Bin only

Which flip-flop is most efficient to implement counters in Verilog?

• SR flip-flop

• D flip-flop

• JK flip-flop

• T flip-flop

If a T flip-flop receives continuous clock pulses with T = 1, the output will:

• Remain constant

• Reset to 0 always

• Toggle between 0 and 1

• Produce unpredictable results

A 2:1 multiplexer can be used to implement:

• XOR gate

• NOT gate

• Any Boolean function

• NAND gate

In the 4×1 multiplexer, if S1S0 = 10, which input is selected?

• I0

• I1

• I2

• I3

A shift register is mainly used for:

• Error detection

• Data storage and transfer

• Frequency division

• Performing subtraction

Which counter produces a sequence like 1000 → 0100 → 0010 → 0001?

• Ripple counter

• Ring counter

• Johnson counter

• Synchronous counter

The main difference between ring counter and Johnson counter is:

• Johnson counter uses feedback of complemented output

• Ring counter is synchronous, Johnson is asynchronous

• Johnson counter cannot be implemented in Verilog

• Ring counter always counts downward