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

There are many advantages of plc - stepper motor , There are many advantage...

There are many advantages of PLC a.The PLC  was specifically designed for harsh  conditions with  electrical  noise magnetic fields vibration  extreme temperatures or humidit

Explain the bidirectional shift registers, Explain the Bidirectional Shift ...

Explain the Bidirectional Shift Registers? A Reversible or A Bidirectional shift register is one in which the data can be shift either left or right. D flip-flops are used by

Digital controller for a steam-turbine driven generator, Q. Digital control...

Q. Digital controller for a steam-turbine driven generator? Figure illustrates the basic elements of a minicomputer system in terms of a block diagram for speed and voltage con

Equivalent circuit of unijunction transistor, Equivalent Circuit : Th...

Equivalent Circuit : The equivalent circuit of a UJT is shown in fig. The P - N junction represented in the emitter by a diode. Silicon bar being lightly doped has a high res

Determine the expected voltage levels at the output, The subsequent voltage...

The subsequent voltage-source multiplying DAC is to be utilized to convert the digital data stream "11" and "01" to an analog signal.  It has 2-bit inputs and hence is capable of c

Determine the number of bits of a natural binary encoder, Determine the num...

Determine the number of bits of a natural binary encoder that works with the quantizer: a) If the extreme levels are ±3.1 V, with a step size of 0.2 V. (b) If there are 128 q

Explain two types of materials that are formed after doping, Explain the tw...

Explain the two types of materials that are formed after doping. Depending on the impurity added, extrinsic semiconductors can be then subdivided in two types of class: N-ty

OSILATOR, COULD U INTERDUCE AN OSILATOR THAT MAKES TRIANGULAR AND SIN WAVE?...

COULD U INTERDUCE AN OSILATOR THAT MAKES TRIANGULAR AND SIN WAVE?

Estimate the maximum number of conversions, Q. The speed of an 8-bit A/D co...

Q. The speed of an 8-bit A/D converter is limited by the counter, which has a maximum speed of 4 × 10 7 counts per second. Estimate the maximum number of A/D conversions per secon

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