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

Determine the base current, Q. A transistor has a base current i B = 25 µA...

Q. A transistor has a base current i B = 25 µA, α = 0.985, and negligible ICBO. Find β, iE, and i .

Intrinsic material, Int r insic Material A perfect semicon...

Int r insic Material A perfect semiconductor crystal with no impurities or lattice defects. No carriers at 0 K, since the valence band is completely full and t

Orthogonal frequency division multiplexing, CURRENTLY, orthogonal frequency...

CURRENTLY, orthogonal frequency division multiplexing (OFDM) is emerging as the preferred modulation technique in modern high data rate broadband wireless mobile communication syst

Asynchronous and synchronous logic design, One of the simplest circuits is ...

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

Real power sources - overview, We have seen that a practical power source m...

We have seen that a practical power source may be modelled by an ideal constant voltage source in series with a resistor - a Thevenin equivalent circuit Alternati

How can we prove that radio waves are sine waves, What makes them sine? ...

What makes them sine? Ans) Fourier tells that only a sine wave has no harmonic content. The math works out that if you have any wave shape other than a sign wave, you can brea

Single Phase Induction Motor, How do I connect a Capacitor on the machine i...

How do I connect a Capacitor on the machine if it has a start mechanism

Psuedo code, Ask questiIn a right triangle, the square of the length of one...

Ask questiIn a right triangle, the square of the length of one side is equal to the sum of the squares of the lengths of the other two sides. Stephanie has the integer lengths of t

How single stepping can be done in 8086, How single stepping can be done in...

How single stepping can be done in 8086? By setting the Trace Flag (TF) the 8086 goes to single-step mode. In this mode, after the implementation of every instruction s 8086 ge

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