Pic16f84a

Discussion in 'The Projects Forum' started by ching fong kee, Aug 4, 2010.

  1. ching fong kee

    Thread Starter Member

    Jun 23, 2010
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    Hi, everyone
    is it possible the PIC16F84A operate at 1V as minimum operating voltage?
     
  2. BMorse

    Senior Member

    Sep 26, 2009
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    No, the PIC16F84A has a minimum of 2 volt operating voltage...
     
  3. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
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    huh??
    but i test with my PIC
    this is show the input pins when there is given to 1 volts, the LEDs that connected at output pins will be light up..
     
  4. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    Are you asking then if you can use 1 volt to trigger an input to the pic or to run the pic off of 1 volt???

    B. Morse
     
  5. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
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    No, i means is
    when the 1Volts to the input port pins , the PIC will treat its as digital '1'.
     
  6. mcgyvr

    AAC Fanatic!

    Oct 15, 2009
    4,771
    971
    The recommended minimum operating voltage is 2V... Why are you only supplying it 1V?
     
  7. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    Yes, that is correct, for TTL input logic high will be 2V or higher, but if using schmitt input buffer then .8/.9 V will be a logic high....


    PIC16F84A Inputs.PNG
    B. Morse
     
  8. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
    0
    Because my sensor output will be connected to the input pins of my PIC.
    When the output voltage of my sensor is reached 1Volts...the LED at output is turn on..
     
  9. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
    0
    but the pins that i connect is RA0 but still is TTL right?
     
  10. BMorse

    Senior Member

    Sep 26, 2009
    2,675
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    Yes RA0 is TTL, RA4 is a schmitt trigger input....

    But since a logic low for TTL input buffer is less than or equal to .8 V then anything higher than .8 will be a logic 1.


    B. Morse
     
  11. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
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    Means the Logic high for all the input port will be the same as the RA4?
     
  12. BMorse

    Senior Member

    Sep 26, 2009
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    According to the datasheet no, but, in reality it should work since your input level is higher than a logic low, You may run into some issues later on if you still want to use RA0 as the input, I would switch the input to RA4 to minimize the risk of not getting the proper voltage to switch the input from 1 volt. Most TTL devices I have worked with in conjunction with a PIC, I have always made sure my logic high was atleast equal to 1.8V...

    B. Morse
     
  13. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
    0
    ooo
    i see...thx a lot for guide ya..
    i think i will switch my input to RA4..
     
  14. tom66

    Senior Member

    May 9, 2009
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    BMorse, I think you have misread the datasheet. It states 0.8 Vdd is required, that means 80% of Vdd. If you supply it even the minimum 2V then 1.6V is the minimum guaranteed logic high.
     
  15. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
    0
    hmmm...how come will like that..
    it actually shows 1.2Volts is logic high
     
  16. tom66

    Senior Member

    May 9, 2009
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    That's the minimum guaranteed rating. For example you might not get 1.2V as a logic high at 85°C or with certain batches of chips.
     
  17. ching fong kee

    Thread Starter Member

    Jun 23, 2010
    42
    0
    means is according to the circumference?
    because i'm doing with the final report..
    The operating voltage of PIC that i wrote is from 1V to 5.5V
    i afraid that is unacceptable..
     
  18. tom66

    Senior Member

    May 9, 2009
    2,613
    214
    The RATED operating range is 2V to 5.5V. This is the range Microchip guarantee the chip will work in its full temperature range, at maximum speed and with all the chips that come out of the factory.

    I have seen PIC16F series chips run on a 1.5V battery at 32 KHz, but there's no guarantee whatsoever from Microchip or me that they will work at 4 MHz or 85°C. I have also seen them work on a 9V battery for a few minutes before blowing smoke (literally), and I run the occasional prototype at 6V with few / no problems.
     
  19. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    That is why I suggested to make sure to get atleast 1.8V for a logic high... the 0.8 is a logic low, not High.
     
  20. BMorse

    Senior Member

    Sep 26, 2009
    2,675
    234

    Operating Voltage is not the same as the logic level inputs... Operating Voltage means the power you are using to power the whole circuit i.e. 2 to 5.5 Volts....

    B. Morse
     
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