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# Synchronous and asynchronous clock

Synchronous and asynchronous clock in sequential circuits

Synchronous and asynchronous clock in sequential circuits

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### Synchronous and asynchronous clock

1. 1. SYNCHRONOUS AND ASYNCHRONOUS CLOCK 1 ANINDRA 12/11/2014
2. 2. WHAT IS CLOCK ? 2  A digital clock signal is basically a square wave ANINDRA 12/11/2014
3. 3. CLOCK.... 3  A clock is generated by clock generator.  here the clock generator is oscillator which provides the square wave as output.  clock will be having two levels…  high level (1) and low level (0). ANINDRA 12/11/2014
4. 4. CLOCK …(CONT’D) 4  clock is used in the circuits which having feedback.  it is also is used to avoid glitches.  what is glitch?  glitch is unpredictable output.  some input and for those you expect a known output, but before the output settles to what you expect, you might have one or more transitions that are not suppose to be there. These are called glitches. ANINDRA 12/11/2014
5. 5. CLOCK….(CONT’D) 5 ANINDRA 12/11/2014
6. 6. CLOCK…(CONT’D) 6  because the inputs have to go through different gates and the propagation delay of each can be different. Therefore the results arrive to the final gates in different times  This difference in data arrival results in changes in the output until all signals settle and the output is valid.  If glitches are not eliminated, they will go to the next stage of the circuit and generate more unpredictable results.  To avoid them a clock can be used to time the signals. ANINDRA 12/11/2014
7. 7. CHARACTERISTICS OF CLOCK 7  There are two types of characteristics of clock are :  1. frequency , 2. phase .  ANINDRA 12/11/2014
8. 8. TYPES OF CLOCK…. 8  there are two types of clocks….  synchronous clock. Asynchronous clock ANINDRA 12/11/2014
9. 9. SYNCHRONOUS CLOCK… 9  if two clocks have same phase and the frequency may or may not be same then that clock is called synchronous clock.  To decide it as a synchronous and asynchronous will not depend on the frequency.(because of frequency only speed varies).  it will be decided by the phase of the two clocks.  if the source of two clock is same then the clock be synchronous. ANINDRA 12/11/2014
10. 10. SYNCHRONOUS CLOCK… 10  if the source of the two clocks is different then is there is a chance of asynchronous.  ANINDRA 12/11/2014
11. 11. ASYNCHRONOUS CLOCK… 11  If the two clocks are with different phase and the frequency may or may not be same then the clock is known as asynchronous signal  If the source of the two clocks is different then there is chance of phase difference then it will leads to synchronous clock. ANINDRA 12/11/2014
12. 12. ASYNCHRONOUS CLOCK… 12 ANINDRA 12/11/2014
13. 13. CLOCK…(CONT’D) 13  But due to this asynchronous clock there is chance of glitches.  So, for this we will synchronize the clock before going to process.  To make it as synchronous we use fifo (first in first out).  By avoiding the asynchronous we will get synchronous output and the complete circuit becomes the synchronous circuit. ANINDRA 12/11/2014
14. 14. 14 ANINDRA 12/11/2014