[PDF] IE1204 Digital Design F12: Asynchronous Sequential Circuits (Part 1)





Previous PDF Next PDF



Chapter 22 - Asynchronous Sequential Circuits

We will look at the relation of setup and hold time to the design of the asynchronous circuits that realize flip-flops in more detail in Chapter 23. In 



A DESIGN METHOD OF ASYNCHRONOUS SEQUENTIAL

A systematic asynchronous design method based on a flow diagram is shown. The realization utilizes a so-called phase-register coded lout of 11.



CS8351 DIGITAL PRINCIPLES AND SYSTEM DESIGN UNIT IV

The analysis of asynchronous sequential circuits consists of obtaining a table or a diagram that describes the sequence of internal states and outputs as a 



Asynchronous Sequential Circuits Design

Asynchronous sequential circuits do not use clock signals as synchronous circuits do. Instead the circuit is driven by the pulses of the inputs which means 



Asynchronous Sequential Circuits

The delay elements can be viewed as providing short term memory for the sequential circuit. Page 3. Asynchronous Sequential Circuits. • During the design of 



A Modern Approach to the Asynchronous Sequential Circuit Synthesis

The switching circuit design is composed of the two classes of the devices: combinational circuits and sequential circuits. The class of the sequential circuits.



Pass-transistor asynchronous sequential circuits

Abstract -The vast majority of sequential circuits currently imple- mented with VLSI circuit technology are designed using synchronous design theory.



Design of asynchronous esign of asynchronous sequential circuits

There are two distinct models by which a synchronous sequential logic circuit can be designed. In Mealy Model the output is derived from present state as well 



COE 202: Digital Logic Design Sequential Circuits Part 1

• Latches are useful in asynchronous sequential circuits. • Flip-Flips are built with latches. Page 8. Latches. • A latch is binary storage element. • Can store 



Design of asynchronous esign of asynchronous sequential circuits

There are two distinct models by which a synchronous sequential logic circuit can be designed. In Mealy Model the output is derived from present state as well 



IE1204 Digital Design F12: Asynchronous Sequential Circuits (Part 1)

gates and summarize their delays to a single block with delay ?. Asynchronous sequential circuit: SR-latch with NOR gates. IE1204 Digital Design Autumn2016.



Asynchronous Sequential Circuits

The analysis of asynchronous sequential circuits An asynchronous sequential circuit may become ... Design a gated latch circuit with two inputs G.



Chapter 22 - Asynchronous Sequential Circuits

Design a toggle circuit like the one in Section 22.2 except that pulses on the input alternate over three outputs. 22–6 Three-Way Edge Toggle. Page 12. 394.



State assignments for non-normal asynchronous sequential circuits

designing an asynchronous sequential circuit is obtaining an internal state assignment. The internal state assignment problem consists basically of encoding 



Chapter 9 - Asynchronous Sequential Logic

the behavior of the circuit can be analyzed by observing the stale transition as a function of changes in the input variables. Flow Table. During the design of 



CS8351 DIGITAL PRINCIPLES AND SYSTEM DESIGN UNIT IV

The memory elements in asynchronous sequential circuits are either unclocked flip-flops (Latches) or time-delay elements. 3. Page 4. S No. Synchronous 



Chapter 9 Asynchronous Sequential Logic Outline

Asynchronous Sequential Circuits. ? Analysis Procedure. ? Circuits with Latches. ? Design Procedure. ? Reduction of State and Flow Tables.



Using Petri Nets in the Design Process for Interacting Asynchronous

Each asynchronous sequential circuit can be described by a state tranllition graph and the .'~e . ign of the circuit froro the given graph is routine.



Asynchronous Sequential Circuits

The delay elements can be viewed as providing short term memory for the sequential circuit. Page 3. Asynchronous Sequential Circuits. • During the design of 

IE1204 Digital Design

F12: Asynchronous

Sequential Circuits

(Part 1)

Masoumeh(Azin) Ebrahimi (masebr@kth.se)

Elena Dubrova (dubrova@kth.se)

KTH / ICT / ES

BV pp. 584-640This lecture

IE1204 Digital Design, Autumn2016

Asynchronous Sequential

Machines

An asynchronous sequential machine is

a sequential machine without flip-flops

Asynchronous sequential machines are

constructed by analyzing combinational logic circuits with feedback Assumption: Only one signal in acircuit can change its value at any time

IE1204 Digital Design, Autumn2016

Golden rule

IE1204 Digital Design, Autumn2016

Asynchronous state machines

Asynchronous state machines are used

when it is necessary to keep the information about a state, but no clock is available - All flip-flops and latches are asynchronous state machines - Useful to synchronize events in situations where metastability is/can be a problem

IE1204 Digital Design, Autumn2016

To analyze the behavior of an

asynchronous circuit, we use ideal gates and summarize their delays to a single block with delay ǻAsynchronous sequential circuit:

SR-latch with NOR gates

IE1204 Digital Design, Autumn2016

R S

QYyDelayIdeal gates

(Delay = 0)Q aR

SSR-latch

By using a delay block, we can treat

- y as the current state - Y as the next stateAnalysis of a sequential asynchronous circuit

IE1204 Digital Design, Autumn2016

R S QYy

Thus, we can produce a state table where the

next state Y depends on the inputs and the current state yState table

IE1204 Digital Design, Autumn2016

R S QY y)(ySRY

State table

IE1204 Digital Design, Autumn2016

)(ySRYPresent

Nextstate

state

SR= 0001 1011

y YYYY

0001011010

ySRYRSyFrom statefunction to truth tableNote: BV usesthisbinary code

Since we do not have flip-flops, but only

combinational circuits, a state change can cause additional state changes

A state is

- stable if Y(t) = y(t + ǻ) - unstable if Y(t) y(t + ǻ)Stable states

IE1204 Digital Design, Autumn2016

Present

Nextstate

state

SR= 0001 1011

y YYYY

0001011010

yYstable

Stable states (next state = present state) are

circledExcitation table

IE1204 Digital Design, Autumn2016

Present

Nextstate

state

SR= 0001 1011

y YYYY

0001011010R

S QYy 00 0 10R S QYy 10 0 01

When dealing with asynchronous

sequential circuits, a different terminology is used - The state table calledflow table - The state-assigned state table is called excitation tableTerminology

IE1204 Digital Design, Autumn2016

Flow table (Moore)

IE1204 Digital Design, Autumn2016

Present

NextstateOutput

state

SR= 0001 1011Q

AAABA0

BBABA1

1000

11010010

A0 B1

1101SR

Flow Table (Mealy)

IE1204 Digital Design, Autumn2016

Present

NextstateOutput,Q

state

SR = 0001 1011 00 01 1011

AAABA000

BBABA11-

-10/1

00/111/0

01/000/010 /-

AB 01-

11-SR/ QDo not care ('-') has been chosen for output decoder since output changes

directly after the state transition (basic implementation)

Asynchronous Moore compatible

IE1204 Digital Design, Autumn2016

Asynchronous sequential circuits have similar

structure as synchronous sequential circuits

Instead of flip-flops one have a "delay block"

R S QYy 10 01 0

Asynchronous Mealy compatible

IE1204 Digital Design, Autumn2016

Asynchronous sequential circuits have similar

structure as synchronous sequential circuits

Instead of flip-flops one have a "delay block"

Analysis of Asynchronous Circuits

The analysis is done using the following steps:

1)Replace the feedbacks in the circuit with a

delay element.The input of the delay element represents the next state Y while the output y represents the current state.

2) Find out thenext-state and output expressions

3) Set up the correspondingexcitation table

4) Create aflow tableand replace the encoded

states with symbolic states

5) Draw astate diagramif necessary

IE1204 Digital Design, Autumn2016

D-latch state function

IE1204 Digital Design, Autumn2016

Q 1D C1QD CQ D CYy CyCDY

Master-slave D flip-flop is designed

using two D-latchesExample

Master-slave D flip-flop

IE1204 Digital Design, Autumn2016

D ClkQQ D CQ ysymMasterSlaveQ D ClkQQ s ssmm yQCyDCYyCCDY

The equations for the next state:

From these equations, we can directly

deduce excitation tableExcitation table

IE1204 Digital Design, Autumn2016

Present

Nextstate

state

CD= 0001 1011Output

y mys YmYsQ

0000 00 00100

0100 00 01111

1011 11 00 100

1111 11 01 111s

ssmm yQCyDCYyCCDY

Excitation table

We define four states S1, S2, S3, S4

and get the following flow tableFlow table

IE1204 Digital Design, Autumn2016

Present

NextstateOutput

state

CD= 00 01 1011Q

S1S1 S1 S1S30

S2S1 S1 S2S41

S3S4 S4 S1 S30

S4S4S4S2S41Present

Nextstate

stateCD= 00 01 1011Output y mys YmYsQ

0000 00 00100

0100 00 01111

1011 11 00 100

11111101111

Excitation table

Flow table

Remember: Only one input can be

changed simultaneously

Thus, some transitions never occur!Flow table

quotesdbs_dbs17.pdfusesText_23
[PDF] design of experiments pdf

[PDF] design of iir and fir digital filters

[PDF] design of iir filters

[PDF] design of machine tools by basu pdf

[PDF] design pattern tutorialspoint

[PDF] design pattern bits

[PDF] design pattern java

[PDF] design pattern library c++

[PDF] design pattern online test

[PDF] design pattern textbook

[PDF] design patterns by tutorials pdf

[PDF] design patterns by tutorials source code

[PDF] design patterns cheat sheet pdf

[PDF] design patterns classification

[PDF] design patterns exam questions