Asynchronous and synchronous logic design, Electrical Engineering

Assignment Help:

One of the simplest circuits is the asynchronous or ' ripple' counter. Below is shown the circuit diagram of a simple 3 stage ripple counter.

1234_Asynchronous and Synchronous logic design.png

The operation of this circuit is based on the fact that the truth table for the JK flip flop is only valid if the clock waveform is falling, i.e. 1->0. Assume the outputs are all zero, the flip flops will not change until the clock on each flip flop falls. The clock in waveform has just fallen  ,since the JKa inputs are logic '1' the device will toggle and the output will invert i.e. Qa=1. Flip flop B will not change because the clock waveform on B has risen    (0->1) and these devices only functions on a falling edge. The clock in waveform has fallen again, so Qa toggles again (i.e. Qa =0), this has just produced a falling clock on JKb and Qb toggles (i.e. Qab=1) .The device has just counted from 000-> 001->010.

960_Asynchronous and Synchronous logic design1.png

The circuit is called a ripple counter because the clock pulse is slowly rippling through the JK's, hence asynchronous (Not at the same time!) .The limitations of the asynchronous counter is the speed of operation. A rough formula for the maximum speed is when the clock changes before the output changes i.e.

      F =  1 / n x propagation delay
 
   where n = number of stages, propagation delay of one JK

A better technique is to use a synchronous design where all the JK are clocked together so the maximum frequency is only limited by the propagation delay of 1 JK.  

59_Asynchronous and Synchronous logic design2.png

 
The circuit appears to be complex in design, however it is easily realised by using state diagrams. The maximum frequency of operation is again roughly calculated by considering the frequency at which the output just changes before the clock in changes.
    
      F = 1/ Propagation delay


Related Discussions:- Asynchronous and synchronous logic design

Obtain an expression for b, Q. Consider an infinitely long, straight wire (...

Q. Consider an infinitely long, straight wire (in free space) situated along the z-axis and carrying current of I A in the positive z-direction. Obtain an expression for ¯B everywh

Find the impedance of the series combination, Q. An RL series circuit carri...

Q. An RL series circuit carries a current of 0.02 cos 5000t A. For R = 100  and L = 20 mH, find the impedance of the series combination and determine the voltage across the series

Explain the parallel in - parallel out shift registers, Explain the Paralle...

Explain the Parallel In - Parallel Out Shift Registers? For "parallel in - parallel out" shift registers all data bits show on the parallel outputs immediately following the si

Registers - microprocessors architecture , Registers Various  register...

Registers Various  registers  shown in figure  are discussed  below  in detail.

Signals and spectral analysis, Q. Signals and spectral analysis? Figure...

Q. Signals and spectral analysis? Figure shows the functional block diagram of a signal-processing system. The information source may be a speech (voice), an image (picture), o

Load stack pointer - stack operations , Load Stack Pointer This  inst...

Load Stack Pointer This  instruction loads the stack  pointer  register with the 16 - bit  data specified in the   instruction. The 16 - bit  data. When  stored in sp  registe

Obtain a thevenin equivalent circuit, Q. (a) Obtain a Thevenin equivalen...

Q. (a) Obtain a Thevenin equivalent circuit at terminals A-B in the circuit. (b) What impedance ¯ZL, when connected to A-B, produces maximum power in ¯ZL? (c) Find the val

Explain radio and television broadcasting, Q. Explain Radio and Television ...

Q. Explain Radio and Television Broadcasting? Radio (AM and FM) and television broadcasting are the most familiar forms of communication via analog transmission systems. The re

What is induction machines, Q. What is Induction machines? We shall fir...

Q. What is Induction machines? We shall first consider polyphase induction motors and then single-phase induction motors. The polyphase induction motors used in industrial appl

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd