T0CKI High Pulse Width delay exist 0.5TCY + 20

Discussion in 'Embedded Systems and Microcontrollers' started by micropad, Feb 20, 2012.

  1. micropad

    Thread Starter Member

    Dec 24, 2011
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    Hi All, need helps
    T0CKI High Pulse Width delay exist 0.5TCY + 20 (No Prescaler) and With Prescaler 10ns. I can not understand the mechanism how delay reduce with Prescaler, please explain


     
  2. ErnieM

    AAC Fanatic!

    Apr 24, 2011
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    Take a deep look at your TIMER0 WITH SHARED PRESCALE BLOCK DIAGRAM.

    When T0CKI is not used with the prescaler there is a Synchronizing circuit based off Fosc/4. That needs a minimum hi or low time to capture the input.

    When the prescaler output is naturally a square wave so there is one less factor to consider.
     
  3. micropad

    Thread Starter Member

    Dec 24, 2011
    38
    0

    Dear ErnieM
    Thanks a lot for clear reply
    as per your reply, if we insert square wave to TOCKI with out prescaler. what do you think
    Thanks in advance
     
  4. ErnieM

    AAC Fanatic!

    Apr 24, 2011
    7,392
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    Then the T0CKI Period spec must still be met, which is Tcy+20nS.

    So it depends on the clock (Fosc) you are using on that device. (Tcy = 4/Fosc)
     
    micropad likes this.
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