Rest problem 89C2051

Discussion in '8bit Microcontrollers' started by ClueLess, Feb 23, 2008.

  1. ClueLess

    ClueLess Guest

    Hi all

    I am just toying with 89C2051 and I have assembled a program to switch
    on a series of LEDs using the rl a instruction. The program works well
    on the simulator. But I cannot make it work on the breadboard.

    The problem is with the reset. I am using an available 32.768kHz
    crystal, I have used the standard 33pf caps too.

    On the reset pin I have tried 1 uf, 10uf capacitors and also
    resistances of various values to the ground from the reset pin. Still
    no go.

    Can someone in the know among you help me with some leads?

    Thanks for your time and attention

    ClueLess
























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    ClueLess, Feb 23, 2008
    #1
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  2. ClueLess

    Eeyore Guest

    ClueLess wrote:

    > Hi all
    >
    > I am just toying with 89C2051 and I have assembled a program to switch
    > on a series of LEDs using the rl a instruction. The program works well
    > on the simulator. But I cannot make it work on the breadboard.
    >
    > The problem is with the reset. I am using an available 32.768kHz
    > crystal, I have used the standard 33pf caps too.
    >
    > On the reset pin I have tried 1 uf, 10uf capacitors and also
    > resistances of various values to the ground from the reset pin. Still
    > no go.
    >
    > Can someone in the know among you help me with some leads?


    Why do you think the problem is with the reset ?

    It's only 2 components. You can hardly go wrong ! How have you connected
    it ?

    Graham
     
    Eeyore, Feb 23, 2008
    #2
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  3. ClueLess

    Eeyore Guest

    ClueLess wrote:

    > I am using an available 32.768kHz
    > crystal, I have used the standard 33pf caps too.


    I'd check that the watch crystal is designed to be used with 33pF caps.
    The first one I looked at is designed for use with 12pF caps.

    Graham
     
    Eeyore, Feb 23, 2008
    #3
  4. ClueLess

    ClueLess Guest

    On Sat, 23 Feb 2008 16:07:40 +0000, Eeyore
    <> wrote:

    >I'd check that the watch crystal is designed to be used with 33pF caps.
    >The first one I looked at is designed for use with 12pF caps.



    Since I did not have a 12pf cap handy I tried with a 4 mHz crystal
    with 33pf caps. Still no go. As I said the code works very well in the
    simulator.

    Any more suggestions?

    Thanks for taking time to help me

    ClueLess




































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    ClueLess, Feb 24, 2008
    #4
  5. ClueLess

    ClueLess Guest

    On Sat, 23 Feb 2008 16:07:40 +0000, Eeyore
    <> wrote:

    >I'd check that the watch crystal is designed to be used with 33pF caps.
    >The first one I looked at is designed for use with 12pF caps.



    Since I did not have a 12pf cap handy I tried with a 4 mHz crystal
    with 33pf caps. Still no go. As I said the code works very well in the
    simulator.

    Any more suggestions?

    Thanks for taking time to help me

    ClueLess

    PS: Did not see this after several hours. So posting again :-(


































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    ClueLess, Feb 25, 2008
    #5
  6. ClueLess

    ClueLess Guest

    On Sat, 23 Feb 2008 16:07:40 +0000, Eeyore
    <> wrote:

    >I'd check that the watch crystal is designed to be used with 33pF caps.
    >The first one I looked at is designed for use with 12pF caps.


    Well, it started working when I caught hold of the crystal with my
    fingers :-(

    True, it seems to want more capacitor. But it is totally not in
    agreement with what I have read.

    How this can be?

    ClueLess






































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    ClueLess, Feb 26, 2008
    #6
  7. ClueLess

    Eeyore Guest

    ClueLess wrote:

    > Eeyore wrote:
    >
    > >I'd check that the watch crystal is designed to be used with 33pF caps.
    > >The first one I looked at is designed for use with 12pF caps.

    >
    > Well, it started working when I caught hold of the crystal with my
    > fingers :-(


    You mean it's OK now ? Good to hear.


    > True, it seems to want more capacitor.


    I expected it to want less capacitance actually !


    > But it is totally not in agreement with what I have read.
    >
    > How this can be?


    Do you have the manufacturer's data for that specific crystal you are using
    ? If not, you need to get it.

    Beware of things like stray capacitance from PCB traces and also it may be a
    good idea to ground the cystal's metal can.

    Graham
     
    Eeyore, Feb 26, 2008
    #7
  8. ClueLess

    ClueLess Guest

    On Tue, 26 Feb 2008 19:15:14 +0000, Eeyore
    <> wrote:

    >Do you have the manufacturer's data for that specific crystal you are using
    >? If not, you need to get it.


    The data sheet says 12.5 pf which I do not have at the moment,
    unfortunately. I will have to order it.

    Meantime I modified the program to work with a 4 mHz crystal and 33 pf
    caps and it worked first shot.

    So it is only the crystal interfacing - the key is in the caps, I
    think.

    I will post the results once I get hold of the 12.5 pf stuff.

    Thanks for your continued interest in helping me


    ClueLess



























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    ClueLess, Feb 28, 2008
    #8
  9. ClueLess

    ClueLess Guest

    On Sat, 23 Feb 2008 20:37:32 +0530, ClueLess
    <> wrote:

    >The problem is with the reset. I am using an available 32.768kHz
    >crystal, I have used the standard 33pf caps too.



    Hi Graham

    I got a clue from someone in the 8052.com to insert a 300k resistor
    between the crystal and the xtal2 pin. And it worked.

    Problem solved. And again thanks for your interest.

    ClueLess
































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    ClueLess, Feb 28, 2008
    #9
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