5 Sequential circuit descriptions

Question 1

What are sequential circuits?

Answer 1

Sequential circuits act as storage elements and have memory. These circuits can store, retain and retrieve information when needed.

Question 2

Block diagram for a Asynchronous sequential circuit?

Answer 2

Question 3

Block diagram for a synchronous sequential counter?

Answer 3

Question 4

Latches?

Answer 4

Latches are useful for storing binary information and for the design of asynchronous sequential circuits. The output of a latch is affected as soon as the inputs change.

Question 5

Flip-Flops?

Answer 5

Flip-flops are part of synchronised sequential circuits. Flip-flops employ a common clock. The state of the flip-flop changes when the pulse, from the clock, goes from high to low or low to high.

Question 6

Syntax for a latch?

Answer 6

Question 7

How are latches used to store information?

Answer 7

Question 8

The uses of latches in asynchronous and synchronous circuits?

Answer 8

Latches are used in asynchronous circuits to store state.

Always avoid latches in synchronous circuits.

Question 9

Flip flop setup(posedge)?

Answer 9

Question 10

Flip Flop setup(negedge)?

Answer 10

Question 11

Blocking assignment?

Answer 11

Blocking assignment is performed using “=“. This assignment blocks the flow of the program during the execution of each statement. Blocking assignments are used for combinatorial logic.

Question 12

Nonblocking assignment?

Answer 12

Nonblocking assignment is performed using “<=“. This assignment does not block the flow of the program, all statements are evaluated, scheduled and executed at the end of the always block. Nonblocking assignments are used for flip-flops and registers

Question 13

Example Full adder with blocking assignment?

Answer 13

Question 14

Example Full adder with nonblocking assignment?

Answer 14

Question 15

Full adder with blocking, output?

Answer 15

Question 16

Full adder with nonblocking, output?

Answer 16

Question 17

How are registers created with more than one bit?

Answer 17

Question 18

What is the concatenation operator?

Answer 18

In SystemVerilog, shift registers require the concatenation operator { }, which combines groups of bits into a bus for their manipulation, e.g., shift, rotate, swap, repeat.

Question 19

Syntax required for

Rotate, SWap and repeat shifts

Answer 19

Rotate right: Reg <= { Reg[14:0], Reg[15] };

Swap bytes: Reg <= { Reg[7:0], Reg[15:8] };

Repeat: Reg <= { 2{ Reg[7:0] } };

Question 20

Example code for shifting in parrallel?

Answer 20

Question 21

Simulation clocks?

Answer 21

Question 22

What is a synchronous reset?

Answer 22

In synchronous resets, assignments to the outputs of the digital system will take place on the next rising edge of the clock.

Question 23

What is an asynchronous reset?

Answer 23

In asynchronous resets, assignments to the outputs of the digital system will take place immediately. The update process do not need to wait until the next rising edge of the clock

Question 24

Synchronous Reset implemented in logic?

Answer 24

Question 25

Asynchronous Reset implemented in logic?

Answer 25