[SI-LIST] Re: LA probes

Anand, if a static logic high level is getting dragged down, then you 
have some fundamental problem like a terminator enabled in the probe or 
perhaps the FPGA input buffer that you do not intend or even a trace 
short.  First find out if this is due to the LA or not.  If the problem 
appears only with the LA connected then check your manuals to insure you 
have:  a correctly selected and functioning probe head, that is set-up 
properly.  If the problem appears without the LA connected, then you 
likely have:

* Misprogrammed FPGA that has terminators enabled within the FPGA I/O cells
* Bus contention
* A wiring problem

Steve

SRINIVASAN ANAND-B06739 wrote:
> I have mapped to CMOS logic family. The probe impedance is 20K. I am
> seeing a voltage of 2.0 V on a static pin on which I was expecting 3.3V.
>
>
> -----Original Message-----
> From: olaney@xxxxxxxx [mailto:olaney@xxxxxxxx]=20
> Sent: Monday, July 30, 2007 12:00 PM
> To: prajitsnair@xxxxxxxxx
> Cc: SRINIVASAN ANAND-B06739; si-list@xxxxxxxxxxxxx
> Subject: Re: [SI-LIST] Re: LA probes
>
> Does the logic analyzer allow you to specify the logic family
> parameters?
>  You might have the wrong setting, for instance PECL loading on a CMOS
> signal.
>
> Orin
>
> On Mon, 30 Jul 2007 15:19:39 +0900 "PRAJIT S  NAIR"
> <prajitsnair@xxxxxxxxx> writes:
>   
>> Dear Anand
>> It may be happening because of probe loading. Please check your Probe=20
>> Capacitance, Frequency of Operation and also Load impedance.
>> =20
>> =20
>> Best Regards
>> Prajit
>> =20
>> =20
>> On 7/30/07, SRINIVASAN ANAND-B06739 <anand.srinivasan@xxxxxxxxxxxxx>
>> wrote:
>>     
>>> Content-Type: text/plain;
>>>        charset=3D"us-ascii"
>>> Content-Transfer-Encoding: quoted-printable Hi All, I have a=20
>>> problem. Given below is a topology that i have.=3D20
>>>
>>>
>>>
>>> =3D20
>>>
>>> =3D20
>>>
>>> I have a bidirectional bus which connects a FPGA to the CHIP. The=20
>>> distance between them is 2 inches. Now to probe this bus, i have
>>>       
>> the
>>     
>>> signals coming out to the right at a distance of about 6 inches.=20
>>>       
>> Note
>>     
>>> that i am using active probes to probe this interface and there
>>>       
>> are NO
>>     
>>> buffers on the line between the chip and LA probes. Now the
>>>       
>> problem is
>>     
>>> that when the LA is plugged in I find that the strength of the
>>>       
>> signals
>>     
>>> driven by the chip comes down from 3.3V to 2V. Without the LA
>>>       
>> plugged,
>>     
>>> the signal strength remains intact. Could anyone help me in=20
>>> understanding this? If a solution is possible to get around this,
>>>       
>> it
>>     
>>> will be great.
>>>
>>> =3D20
>>> Regards,
>>> Anand
>>>
>>> =3D20
>>>
>>> =3D20
>>>
>>>
>>>
>>>
>>> -- Binary/unsupported file stripped by Ecartis --
>>> -- Type: image/jpeg
>>> -- File: Outlook.jpg
>>> -- Desc: Outlook.jpg
>>>
>>>
>>> ------------------------------------------------------------------
>>> To unsubscribe from si-list:
>>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject
>>>       
>> field
>>     
>>> or to administer your membership from a web page, go to:
>>> http://www.freelists.org/webpage/si-list
>>>
>>> For help:
>>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>>>
>>>
>>> List technical documents are available at:
>>>                http://www.si-list.net
>>>
>>> List archives are viewable at:
>>>                http://www.freelists.org/archives/si-list
>>> or at our remote archives:
>>>                http://groups.yahoo.com/group/si-list/messages
>>> Old (prior to June 6, 2001) list archives are viewable at:
>>>                http://www.qsl.net/wb6tpu
>>>
>>>
>>>
>>>       
>> =20
>> =20
>> ------------------------------------------------------------------
>> To unsubscribe from si-list:
>> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>> =20
>> or to administer your membership from a web page, go to:
>> http://www.freelists.org/webpage/si-list
>> =20
>> For help:
>> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>> =20
>> =20
>> List technical documents are available at:
>>                 http://www.si-list.net
>> =20
>> List archives are viewable at:    =20
>>                 http://www.freelists.org/archives/si-list
>> or at our remote archives:
>>                 http://groups.yahoo.com/group/si-list/messages
>> Old (prior to June 6, 2001) list archives are viewable at:
>>                  http://www.qsl.net/wb6tpu
>>  =20
>> =20
>> =20
>> =20
>>     
> ------------------------------------------------------------------
> To unsubscribe from si-list:
> si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field
>
> or to administer your membership from a web page, go to:
> http://www.freelists.org/webpage/si-list
>
> For help:
> si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field
>
>
> List technical documents are available at:
>                 http://www.si-list.net
>
> List archives are viewable at:     
>               http://www.freelists.org/archives/si-list
> or at our remote archives:
>               http://groups.yahoo.com/group/si-list/messages
> Old (prior to June 6, 2001) list archives are viewable at:
>               http://www.qsl.net/wb6tpu
>   
>
>
>
>   


-- 
Steve Weir
Teraspeed Consulting Group LLC 
121 North River Drive 
Narragansett, RI 02882 

California office
(408) 884-3985 Business
(707) 780-1951 Fax

Main office
(401) 284-1827 Business 
(401) 284-1840 Fax 

Oregon office
(503) 430-1065 Business
(503) 430-1285 Fax

http://www.teraspeed.com
This e-mail contains proprietary and confidential intellectual property of 
Teraspeed Consulting Group LLC
------------------------------------------------------------------------------------------------------
Teraspeed(R) is the registered service mark of Teraspeed Consulting Group LLC

------------------------------------------------------------------
To unsubscribe from si-list:
si-list-request@xxxxxxxxxxxxx with 'unsubscribe' in the Subject field

or to administer your membership from a web page, go to:
http://www.freelists.org/webpage/si-list

For help:
si-list-request@xxxxxxxxxxxxx with 'help' in the Subject field


List technical documents are available at:
                http://www.si-list.net

List archives are viewable at:     
                http://www.freelists.org/archives/si-list
or at our remote archives:
                http://groups.yahoo.com/group/si-list/messages
Old (prior to June 6, 2001) list archives are viewable at:
                http://www.qsl.net/wb6tpu

Other related posts: