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 is piconet, A collection of devices connected by Bluetooth technology ...

A collection of devices connected by Bluetooth technology in an ad hoc fashion.

What is the need of modem in data communication, Q. What is the need of MOD...

Q. What is the need of MODEM in data communication? Need of Modem: Modems are used to interface computers, computer networks in addition to other terminal equipment to teleco

Define time constant, Time constant Time constant, defines as time for ...

Time constant Time constant, defines as time for current achieve maximum (IM) if this maintain the early promotion rate current.

Connection of shunt capacitors - across individual customers, Connection of...

Connection of Shunt Capacitors - Across Individual Customers The most appropriate manner of improving PF of the distribution system and thereby reducing line losses is to link

Explain indexed addressing in 8051, Probelm: (a) Explain indexed addre...

Probelm: (a) Explain indexed addressing in 8051. (b) How does the 8051 distinguish between a byte address and a bit address? (c) How do open-loop and closed loop appli

Compute the minimum line current for the motor, A three-phase, wye-connecte...

A three-phase, wye-connected, four-pole, 400- V, 60-Hz, 15-hp synchronous motor has a synchronous reactance of 3  per phase and negligible armature resistance. The data for its no

Find the current flow through resistor using norton theorem, Use Norton Th...

Use Norton Theorem, find the current flow through resistor R=10Ω.

Domestic financial system, Q. "Developing countries could delay opening the...

Q. "Developing countries could delay opening the capital account until the domestic financial system is strong enough to withstand the sometimes flow of world capital and violen

Explain index mode and base address mode, Explain index mode and base addre...

Explain index mode and base address mode (with examples) available in microprocessors. Index Mode and Base Address Mode: Address supplied through the instruction is adde

Explain the nor gates - microprocessor, Explain the NOR GATES - Microproces...

Explain the NOR GATES - Microprocessor The NOR GATE is an OR gate with the output inverted. Consequently the outputs of a NOR gate would have the opposite states as the outputs o

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