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Hot!Why do we need a 10k resistor connect to the /MCLR?

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KaiMun
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2007/11/19 21:14:38 (permalink)
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Why do we need a 10k resistor connect to the /MCLR?

Why do we need a 10k resistor connect to the /MCLR?
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    Graham2107
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/19 21:35:49 (permalink)
    +1 (1)
    To hold !MCLR high while in use.  If !MCLR is in any way low the processor will reset.
    #2
    bob_barr
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/19 21:36:29 (permalink)
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    In some cases, it's not absolutely required; a direct connection to Vdd will work just as well.
     
    If you're doing In-Circuit Serial Programming (ICSP) or are debugging with the ICD-2 debugger, though, you need it to separate the /MCLR line from the Vdd line. During programming, the /MCLR line rises to around 12 volts. That voltage can't be allowed onto the Vdd power rail.

    While it's always good to learn from one's mistakes, it's much easier to learn from the mistakes of others.
    Please don't PM me with technical questions. I'll be quite happy to help (if I can) on the forums.
    #3
    KaiMun
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/19 22:12:32 (permalink)
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    ok... but in some cases, let say we need to put a resistor...
    to act as a pull-up resistor.. but..
    Y must it be 10K? Can it be another different value?
    #4
    P Lameijn
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/19 22:59:36 (permalink)
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    >> Y must it be 10K?
     
    No, 2k2 to 33 k will do
     
    >> Can it be another different value?
     
    Yes. Lower value will give better protection against resets through spikes and noise; higher value gives lower power use...
     

    Regards,
    Peter
    #5
    bob_barr
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/19 23:30:37 (permalink)
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    Yes. Lower value will give better protection against resets through spikes and noise; higher value gives lower power use...

    Higher values also better limit any possible Vdd rise during programming. I usually use a 22k resistor.

    While it's always good to learn from one's mistakes, it's much easier to learn from the mistakes of others.
    Please don't PM me with technical questions. I'll be quite happy to help (if I can) on the forums.
    #6
    Olin Lathrop
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/20 05:55:49 (permalink)
    +2 (1)
    Y must it be 10K?

    I think you're asking "Why must it be 10K?".  Don't use annoying deliberate misspellings here if you don't want to be dismissed as a clueless moron.
     
    But to answer the question you apparently asked, it doesn't need to be 10Kohms.  My standard value is 20Kohms.  That still provides plenty of noise immunity from coupled spikes (if you have spikes that can change a 20Kohm line from a high to a low you've got a lot more serious problems), but is high enough so that most PIC programmers can overcome it, and it won't dump too much current on Vdd when MCLR is driven to 13V by a PIC programmer.
    #7
    KaiMun
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    RE: Why do we need a 10k resistor connect to the /MCLR? 2007/11/20 19:11:45 (permalink)
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    First of all thank you for all the answer u guys have posted.
    I really appreciates that.
    I believe the purpose of this forum is to share our knowedge between our community and to improve ourself.
    "if we seek, we shall find" and i found it! Thank you so much...
     
    #8
    verminsky
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    Y indeed!! 2007/11/20 19:40:42 (permalink)
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    While I agree that using cell phone texting shortcuts in a forum dedicated to discussing a syntactically critical subject such as micro controller programming is a bit troubling, it seems that many users of this forum are using English as a second language.

    It's dspicable
    #9
    Ron Hayes
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    RE: Y indeed!! 2007/11/20 21:16:44 (permalink)
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    Why do we need a 10k resistor connect to the /MCLR?


    He spelled it right in the first post.

    Personally I hate the shortcuts, they may be fine on a cell phone if you pay per character but here you should be a little more profesional, when I see that crap I think of a child talking. Take the 2 extra seconds and spell it properly, I could care less if you misspell it but at least you tried.

    Ron
    #10
    Olin Lathrop
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    RE: Y indeed!! 2007/11/21 06:09:15 (permalink)
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    it seems that many users of this forum are using English as a second language.

    True, and I can overlook some misspellings, wrong tense, and the like, especially when someone fills in their location and it's not from a english speaking region.  However those kinds of errors are very different from deliberate misspellings coming from just plain laziness and rudeness, such as "y" for "why" and "u" for "you".
    #11
    DSchabel
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    RE: Y indeed!! 2007/11/21 06:26:38 (permalink)
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    ORIGINAL: Olin Lathrop

    it seems that many users of this forum are using English as a second language.

    True, and I can overlook some misspellings, wrong tense, and the like, especially when someone fills in their location and it's not from a english speaking region.  However those kinds of errors are very different from deliberate misspellings coming from just plain laziness and rudeness, such as "y" for "why" and "u" for "you".

    I agree totally.  And I find it annoying that he did this again in thepost immediately after you took him to task for this annoying habit:
    "thank you for all the answer u guys have posted"
    #12
    pgibbons
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    Re: RE: Y indeed!! 2014/08/02 22:02:29 (permalink)
    -1 (1)
    I was using a 3kOhm resistor because the datasheet said, at least 1kOhm (PIC16F753). During programming the Vdd line was pulled up to 7 Volts! I have it disconnected now, just disappointed the datasheet didn't warn of this.
    #13
    ric
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    Re: RE: Y indeed!! 2014/08/02 22:23:15 (permalink)
    +1 (2)
    Why drag up a seven year old topic just to have a whinge at Microchip?
    You never mentioned what programmer you were using.
    I'm surprised you would see 7V on VDD if it is only being pulled up through a 3k3 resistor from MCLR.
    Even if MCLR was at 13V, that is only 1.8mA going through the resistor, not enough to damage anything.
    If the current was higher, then your programmer was putting way too much voltage onto MCLR.
     

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    #14
    pgibbons
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    Re: RE: Y indeed!! 2014/08/03 14:49:19 (permalink)
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    I didn't know the topic was 7 years old. I'm using ICD 3. The PIC has no load, maybe that's why.
    #15
    acharnley
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    Re: RE: Y indeed!! 2019/06/16 05:04:20 (permalink)
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    I was searching for a info and found this thread.

    Using a PICKit 4 and a PIC16F15323 a 10k between MCLR and Vdd causes programming to fail. 

    According to https://microchipdeveloper.com/8bit:lvp in newer devices there is a built-in pull-up resistor so an external one is no longer required.
    #16
    katela
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    Re: RE: Y indeed!! 2019/06/16 15:01:31 (permalink)
    +1 (1)
    acharnley
    I was searching for a info and found this thread.

    Using a PICKit 4 and a PIC16F15323 a 10k between MCLR and Vdd causes programming to fail. 

    According to https://microchipdeveloper.com/8bit:lvp in newer devices there is a built-in pull-up resistor so an external one is no longer required.


    Why not start your own thread instead of digging up this old one which is a bit  different to yours. It's better if you start your own thread and clearly explain what fails, the actual error message you are getting and your connection.

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    #17
    acharnley
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    Re: RE: Y indeed!! 2019/06/20 14:39:15 (permalink)
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    Just saying that the info is out of date - it's now the reverse (don't include one, the WPU will do it for you). 
    #18
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