Rest problem 89C2051

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ClueLess Contact options for registered users 's Avatar (by Gravatar) posted on
February 23, 2008, 3:07 pm
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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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Eeyore Contact options for registered users 's Avatar (by Gravatar) posted on
February 23, 2008, 4:01 pm
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Re: Rest problem 89C2051




ClueLess wrote:

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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


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Eeyore Contact options for registered users 's Avatar (by Gravatar) posted on
February 23, 2008, 4:07 pm
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Re: Rest problem 89C2051




ClueLess wrote:

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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


ClueLess Contact options for registered users 's Avatar (by Gravatar) posted on
February 24, 2008, 1:03 am
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Re: Rest problem 89C2051


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

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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 Contact options for registered users 's Avatar (by Gravatar) posted on
February 25, 2008, 12:44 am
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Re: Rest problem 89C2051


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

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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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Moon Shine Contact options for registered users 's Avatar (by Gravatar) posted on
February 25, 2008, 3:37 am
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Re: Rest problem 89C2051



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Could be alot of things.
Are you declaring variables in ROM space? Would work with emulator.
If you are using a software emulator, make sure you recompile with that
option off.
Are you compiling within ROM space addresses?
Are you using RAM within RAM space limits?
etc...


ClueLess Contact options for registered users 's Avatar (by Gravatar) posted on
February 26, 2008, 2:03 pm
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Re: Rest problem 89C2051


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

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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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Eeyore Contact options for registered users 's Avatar (by Gravatar) posted on
February 26, 2008, 7:15 pm
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Re: Rest problem 89C2051




ClueLess wrote:

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


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I expected it to want less capacitance actually !


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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


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ClueLess Contact options for registered users 's Avatar (by Gravatar) posted on
February 28, 2008, 12:53 am
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Re: Rest problem 89C2051


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

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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 Contact options for registered users 's Avatar (by Gravatar) posted on
February 28, 2008, 9:42 am
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Re: Rest problem 89C2051


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

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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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