Hi all,
 
I have an 8MHz crystal attached to XIN / XOUT of my MSP430F149.
 
In software (IAR C Compiler), I am dividing LFXT1CLK by 8 to give me 1MHz out of
ACLK. 1MHz is indeed present on ACLK but there is also a 40Hz (approx.) square
wave imposed on it!!!.
 
Does anyone know why this is?

	Best regards 
Darren Logan BSc(Hons) 
Development Engineer 
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Quoting Darren Logan <darrenl@darr...>:
> In software (IAR C Compiler), I am dividing
LFXT1CLK by 8 to give me
> 1MHz out of ACLK. 1MHz is indeed present on ACLK but there is also a
> 40Hz (approx.) square wave imposed on it!!!.
>
> Does anyone know why this is?

If you have a digital scope, could you post some captured waveforms?

Also what make/model of scope are you using? I've had aliasing problems
with some of the older digital sampling scopes, depending on the sweep
range setting. Do you notice the 40hz regardless of how fast the scope
is sweeping?

Dave

Have you configured the port for high frequency operation. Normally on a 
'149 you'd pick X2 for your highest frequency crystal.

Al

Darren Logan wrote:

> 
> Hi all,
>  
> I have an 8MHz crystal attached to XIN / XOUT of my MSP430F149.
>  
> In software (IAR C Compiler), I am dividing LFXT1CLK by 8 to give me 1MHz
out of ACLK. 1MHz is indeed present on ACLK but there is also a 40Hz (approx.)
square wave imposed on it!!!.
>  
> Does anyone know why this is?
> 
> 	Best regards 
> Darren Logan BSc(Hons) 
> Development Engineer 
> ________________________________________________________________ 
> 
> 	MICHELL INSTRUMENTS LTD Tel: +44 (0)1223 434 854 
> Nuffield Close Fax: +44 (0)1223 434 895 
> Cambridge e-mail: darrenl@darr... 
> CB4 1SS, UK web: www.michell-instruments.com 
> 
> 	UKAS accredited: 0179 * BS EN ISO9001:2000 registered: Q6284 * Member BCAS
* Investor in People 
> 
> 	--------------------------------- Dew point specialists
--------------------------------- 
> 
> This communication contains information which is confidential and may also
be privileged. It 
> is for the exclusive use of the intended recipient(s). If you are not the
intended recipient(s), 
> please note that any distribution, copying or use of this communication or
the information in 
> it is strictly prohibited. If you have received this communication in
error, please notify the 
> sender immediately and then destroy any copies of it.
> 
>  
> 
> 
> 
> 
> 
> 
> 
> 
> 
> 
> .
> 
>  
> Yahoo! Groups Links
> 
> 
> 
>  
> 
> 
> 
> 

Uytkownik Darren Logan napisa:

>Hi all,
> 
>I have an 8MHz crystal attached to XIN / XOUT of my MSP430F149.
> 
>In software (IAR C Compiler), I am dividing LFXT1CLK by 8 to give me 1MHz
out of ACLK. 1MHz is indeed present on ACLK but there is also a 40Hz (approx.)
square wave imposed on it!!!.
> 
>Does anyone know why this is?
>
>  
>
Hmm, stupid question:
Watchdog timeout?

Albert