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

What are the different types of distributing frames, Q. What are the differ...

Q. What are the different types of distributing frames used in exchanges? Ans: Different distribution  frames  used  in  exchange  are  displayed in  figure.  Each subscribe

Bonding forces and energy bands in solids, Bonding Forces and Energy Bands ...

Bonding Forces and Energy Bands in Solids Electrons are controlled to sets of discrete energy levels in atoms, with large gaps among them in which no energy state is obta

Ins increment register pair instruction , INS  Increment Register Pair Ins...

INS  Increment Register Pair Instruction Contents of the registers pair R P will be  incremented by one  and the  result  will be stored  in the  same  register pair. It is

Field effect transistors, basic configuration of field effect transistors i...

basic configuration of field effect transistors in mplifiers

Atomic structure, State the postulates of Bohr''s atomic model. Write any ...

State the postulates of Bohr''s atomic model. Write any three merits and demerits.

Compute the total capacitance with parallel connection, Compute the total c...

Compute the total capacitance with parallel connection: Three capacitors C 1 , C 2 and C 3 contain capacitance 20 μf, 15 μf, 30 μf, respectively. compute: 1. Charge on ea

Find the t- domain forced response, Consider an RLC series circuit excited ...

Consider an RLC series circuit excited by v(t) = Ve st in the time domain. Assume no initial capacitor voltage or inductive current at t = 0. Draw the transformed network in the s

Kirckoff, How to solve using kcl and kvl

How to solve using kcl and kvl

Illustrate nodal-voltage method, Q. Illustrate Nodal-Voltage Method ? A...

Q. Illustrate Nodal-Voltage Method ? A set of node-voltage variables that implicitly satisfy the KVL equations is selected in order to formulate circuit equations in this nodal

Synchronization, Synchronization:  Whatever type of weep is used, it must ...

Synchronization:  Whatever type of weep is used, it must be synchronized with the signal being measured. Synchronization has to be done to obtain a stationary pattern. This requir

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