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Synchronous and asynchronous reset

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Synchronous and asynchronous reset in sequential circuits..

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Synchronous and asynchronous reset

  1. 1. SYNCHRONOUS AND ASYNCHRONOUS RESET 12/11/2014 ANINDRA 1
  2. 2. WHY RESET IS USED..?  Reset is used to initialize the hardware design of a system and to make system to known state from unknown state. Ex…RESET SIGNAL 12/11/2014 ANINDRA 2
  3. 3. TYPES OF RESETS…. 12/11/2014 ANINDRA 3  Reset is of two types :- 1. Synchronous reset :-- a synchronous reset will reset the circuit at active edge of clock .
  4. 4. ADVANTAGES OF SYNCHRONOUS RESET….  Gives a completely synchronous circuit  Provides filtering for the reset signal, So circuit will not be affected by glitches.  Will meet reset recovery time, as the deassertion will happen within 1 clock cycle 12/11/2014 ANINDRA 4
  5. 5. DISADVANTAGES…  Reset needs to be stretched, if it is not long enough to be seen at the active clock edge.  Requires presence of clock to reset the circuit.  Asynchronous reset may be required if there are 12/11/2014 ANINDRA 5 internal tri state buffers.
  6. 6. DISADVANTAGES…. 12/11/2014 ANINDRA 6  It is slow.  Synthesis will not be able to easily differentiate reset from other signals. So this has to be taken care while doing synthesis. Otherwise it may lead to timing issues.  If there are gated clocks for power saving, this type of reset won’t be suitable.
  7. 7. ASYNCHRONOUS RESET…. 2. Asynchronous reset :-- asynchronous reset will reset the circuit asynchronously i.e no matter with the clock. 12/11/2014 ANINDRA 7
  8. 8. ASYNCHRONOUS RESET ADVANTAGES ….  Reset gets the highest priority. 12/11/2014 ANINDRA 8  It is fast.  Does not require presence of clock to reset the circuit.
  9. 9. DIADVANTAGES…  Reset line is sensitive to glitches.  May have metastability issues 12/11/2014 ANINDRA 9
  10. 10. THANK YOU 12/11/2014 10 ANINDRA

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