RTL Design Engineer Interview Questions and Answers

Mux and De-Mux can be used to implement logic gates.

• Mux can be used to implement OR gate by selecting one of the inputs.

• De-Mux can be used to implement AND gate by selecting one of the outputs.

• Mux and De-Mux can be used together to implement any logic gate.

• Mux and De-Mux can also be used to implement arithmetic circuits like adders and multipliers.

The setup time and hold time in a flipflop are typically set by the designer during the design phase.

• Setup time and hold time are parameters specified by the designer in the flipflop's datasheet.

• The designer ensures that the setup time and hold time requirements are met to prevent timing violations.

• Setup time is the minimum time before the clock edge that the data input must be stable.

• Hold time is the minimum time after the clock edge that the data input must be stable.

To calculate 64*x where x is 32 bit without using operator in Verilog code.

• Use shift left operation to multiply x by 64 (2^6).

• Shift x left by 6 bits to achieve the result.

• Ensure proper handling of overflow or truncation if necessary.

Arbiter FSM in one-client one-master configuration using Verilog

• Implement a Finite State Machine (FSM) in Verilog to control access to a shared resource

• Use a one-hot encoding scheme for state representation

• Ensure only one client can access the resource at a time

• Utilize a priority scheme to determine which client gets access next

A latch is level sensitive and a flip-flop is edge sensitive. Latch changes output as soon as input changes, while flip-flop changes output only on clock edge.

• Latch is level triggered, while flip-flop is edge triggered

• Latch changes output as soon as input changes, while flip-flop changes output only on clock edge

• Latch is asynchronous, while flip-flop is synchronous

• Examples: SR latch, D latch for latch; D flip-flop, JK flip-flop for flip-flop

A 4x1 multiplexer code selects one of four inputs based on select lines.

• Define inputs, select lines, and output in Verilog

• Use conditional statements to select the output based on select lines

• Example: module mux4x1(input [3:0] data, input [1:0] sel, output reg out;)

• Example: always @(*) begin if(sel == 2'b00) out = data[0]; else if(sel == 2'b01) out = data[1]; else if(sel == 2'b10) out = data[2]; else out = data[3]; end

FIFO design in Verilog involves creating a First-In-First-Out buffer for storing and retrieving data.

• Use Verilog code to define a FIFO module with input and output ports.

• Implement logic for writing data into the FIFO and reading data out in sequential order.

• Ensure proper synchronization and handling of full and empty conditions.

• Test the FIFO design using simulation tools like ModelSim.

• Consider parameters like depth, width, and clock frequency for optimal performance.

A mod counter is a counter that counts from 0 to a specified modulus value before resetting to 0.

• Design a counter with a specified number of bits to represent the count value

• Implement logic to increment the count value by 1

• Add logic to reset the count value to 0 when it reaches the modulus value