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From: Patrick Doyle <wpdster AT gmail DOT com>
Date: Mon, 4 Mar 2013 11:58:46 -0500
Message-ID: <CAF_dkJCLJzc7F9HXhxMqkFOA1JxvwCfHTXAGDTF6ty-kXf=bzA@mail.gmail.com>
Subject: Re: [geda-user] Unterminated logic signals
To: geda-user AT delorie DOT com
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On Mon, Mar 4, 2013 at 10:23 AM, Ouabache Designworks <z3qmtr45 AT gmail DOT com>wrote:

>
>
> On Sun, Mar 3, 2013 at 7:14 PM, Patrick Doyle <wpdster AT gmail DOT com> wrote:
>
>> Hello Experts!
>> I have a question for you...
>>
>> I have a PCB I purchased from a vendor that has a 15 pin connector on it,
>> of which only 8 pins have defined functions.  (The functions of the other 7
>> pins are undefined by the manufacturer of the board and may or may not be
>> connected to logic on their board.  I have asked to what those pins are
>> connected, but haven't heard anything back yet).  Of the 8 pins with
>> defined functions, I use only 7.  I have a cable drawing that specifies
>> which 7 pins should be connected at each end of the cable.
>>
>> The problem is, our manufacturing guys built (or allowed a 3rd party to
>> build) cables with all 15  pins in the connector populated.  At the other
>> end, they just cut the unused 8 wires and populated the connector with the
>> 7 signals I use.
>>
>> I am trying to decide whether I need to tell our manufacturing guys to
>> rework the cables or not.  How much do you think it matters that there
>> might be digital logic on the PCB driving signals down those unused wires
>> in my cable?  The cable itself is shielded, but I wonder what sort of cross
>> talk the unterminated signals might cause.  (I also worry a little bit
>> about the clipped ends shorting together, but for the purpose of this
>> question, I'm going to assume (ha ha) that they insulated each end after
>> they clipped it).
>>
>> What do you folks think?
>>
>> --wpd
>>
>>
>
> If you don't fix it and you have any problems at all then you will waste a
> lot of time proving that the problems are not due to these extra wires
> before you move on to find the real issues.
>
>
> John Eaton
>
>
>
> Hi everybody, thanks for the comments and advice.  I think that John's
reply sums up my thoughts on the matter best.

--wpd

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<br><div class=3D"gmail_quote">On Mon, Mar 4, 2013 at 10:23 AM, Ouabache De=
signworks <span dir=3D"ltr">&lt;<a href=3D"mailto:z3qmtr45 AT gmail DOT com" targe=
t=3D"_blank">z3qmtr45 AT gmail DOT com</a>&gt;</span> wrote:<br><blockquote class=
=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px #ccc solid;padd=
ing-left:1ex">

<br><br><div class=3D"gmail_quote"><div><div class=3D"h5">On Sun, Mar 3, 20=
13 at 7:14 PM, Patrick Doyle <span dir=3D"ltr">&lt;<a href=3D"mailto:wpdste=
r AT gmail DOT com" target=3D"_blank">wpdster AT gmail DOT com</a>&gt;</span> wrote:<br><=
blockquote class=3D"gmail_quote" style=3D"margin:0 0 0 .8ex;border-left:1px=
 #ccc solid;padding-left:1ex">


Hello Experts!<div>I have a question for you...</div><div><br></div><div>I =
have a PCB I purchased from a vendor that has a 15 pin connector on it, of =
which only 8 pins have defined functions. =A0(The functions of the other 7 =
pins are undefined by the manufacturer of the board and may or may not be c=
onnected to logic on their board. =A0I have asked to what those pins are co=
nnected, but haven&#39;t heard anything back yet). =A0Of the 8 pins with de=
fined functions, I use only 7. =A0I have a cable drawing that specifies whi=
ch 7 pins should be connected at each end of the cable.</div>




<div><br></div><div>The problem is, our manufacturing guys built (or allowe=
d a 3rd party to build) cables with all 15 =A0pins in the connector populat=
ed. =A0At the other end, they just cut the unused 8 wires and populated the=
 connector with the 7 signals I use.</div>




<div><br></div><div>I am trying to decide whether I need to tell our manufa=
cturing guys to rework the cables or not. =A0How much do you think it matte=
rs that there might be digital logic on the PCB driving signals down those =
unused wires in my cable? =A0The cable itself is shielded, but I wonder wha=
t sort of cross talk the unterminated signals might cause. =A0(I also worry=
 a little bit about the clipped ends shorting together, but for the purpose=
 of this question, I&#39;m going to assume (ha ha) that they insulated each=
 end after they clipped it).</div>




<div><br></div><div>What do you folks think?</div><div><br></div><div>--wpd=
</div><div><br></div></blockquote></div></div><div><br><br>If you don&#39;t=
 fix it and you have any problems at all then you will waste a lot of time =
proving that the problems are not due to these extra wires before you move =
on to find the real issues.<br>


<br><br>John Eaton<br><br>=A0<br></div></div><br>
</blockquote></div>Hi everybody, thanks for the comments and advice. =A0I t=
hink that John&#39;s reply sums up my thoughts on the matter best.<div><br>=
</div><div>--wpd</div><div><br></div>

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