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The nominal HV programming voltage (Vpp) is not always 13 Volt

Discussion in 'Oshonsoft' started by ljcox, Jan 1, 2015.

  1. ljcox

    ljcox Well-Known Member

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    I recently discovered - by looking at some of the files in the MPLAB IDE Device folder (see Program Files (x86)\Microchip\MPLAB IDE\Device) - that the nominal programming voltage (Vpp) is not always 13 Volt. Some examples (taken from the respective .dev files) are shown below - note that the PIC 16F684 is 11 Volt nominal with a maximum of 12 Volt!

    PIC16F84
    vpp (range=12.000-14.000 dflt=13.000)

    PIC16F88
    vpp (range=12.500-13.500 dflt=13.000)

    PIC12F675
    vpp (range=12.750-13.250 dflt=13.000)

    PIC16F684
    vpp (range=10.000-12.000 dflt=11.000)

    PIC16F917
    vpp (range=10.000-12.000 dflt=11.000)

    All of the PIC programming hardware I have seen are designed to apply about 13 Volt. So I don’t know what would happen if one of these was used to programme a 16F684 or a 16F917.

    I recently purchased three 16F684 PICs so I intend to modify my programmer so I can switch it between a 11 and 13 Volt using a jumper shunt.

    One of the programmers I constructed is the dSPIC/PIC Programmer published by Silicon Chip in their May 2008 issue. This one will be easy to modify so I will do it in the new year and post the details in this forum.
     
  2. Ian Rogers

    Ian Rogers Super Moderator Most Helpful Member

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    The original Pickits 2 /3 have a PWM style VPP generator... This means they can generate the correct VPP for the chip chosen..... I wouldn't use any other programmer..... I my opinion, it costs nearly as much to make one as it is to buy one.. Every time I see this topic, someone has had a headache for some reason or another.... For less than £30 why go through the ordeal!!!
     
  3. mvs sarma

    mvs sarma Well-Known Member

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    i remember that above 10.5V , it should work without any issues.the voltage depends on other factors like load on Vtarget and thereby on the Vusb
     
  4. dave

    Dave New Member

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  5. ljcox

    ljcox Well-Known Member

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    It cost me very little to make mine as I had most of the parts on hand.
    I don't find it is a ordeal. All I need to do is add a jumper shunt & a resistor or 2 so I can alter the voltage from 13 to 11 when necessary.

    Thanks for the responses.
     
  6. Colin

    Colin Member

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    Just supply 13.6v via a 10k resistor and each chip will take care of itself.

    You need 13.6v for some chips.
     
  7. koolguy

    koolguy Active Member

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    Hello,
    i am confused with the 2 pins MCLR and VPP.
    how they work?
     
  8. Superdat

    Superdat Member

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    It's the same pin but it has 2 functions.
    MCLR -Master Clear, resets the chip when it goes low so if MCLR is enabled, it needs to be held high via a 10k resistor for the chip to work.
    Vpp is the high voltage mentioned above that is used to initiate programming of the chip.
     

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