Re: JTAG pins

[Ted Firlit <firlit@utmc.aeroflex.com>]

Brooks,

I agree with your points.  We are trying to get support from two
motherboard vendors with which we have found this problem.  I'll give
them a couple of days to respond before letting the user's group know
the names of the vendors and motherboard model numbers.

regards,

Ted Firlit

Lame Brooks-G14738 wrote:
> 
> I strongly suggest that we try to enforce the compatibility intent of
> specifications by making it widely known (first to the source) when there is
> a real problem due to a manufacturer not adhering to the spec(s).  What is
> the mfg and model of the non-compliant motherboard.  Distributors should
> also be informed.
> 
> I just want the products I buy to work!    -- BrooksL      :)
> 
> > -----Original Message-----
> > From: Olaf Birkeland [mailto:Olaf.Birkeland@fast.no]
> > Sent: Monday, 03 September, 2001 00:03
> > To: pci-sig@znyx.com
> > Cc: ted.firlit@utmc.aeroflex.com
> > Subject: RE: JTAG pins
> >
> >
> > > -----Original Message-----
> > > From: firlit@utmc.aeroflex.com [mailto:firlit@utmc.aeroflex.com]
> > > Sent: Friday, August 31, 2001 20:18
> > > To: pci-sig@znyx.com
> > > Subject: JTAG pins
> > >
> > >
> > > Hello,
> > >
> > > I have just recently come across a fairly new motherboard
> > which has the
> > > PCI connector TMS signal pulled down to ground with a 1K resistance.
> > > This is crippling to my PCI card, since I use the JTAG signals for
> > > production test of the card (and this pulldown puts my PCI interface
> > > device into JTAG mode).  This brings me to 2 questions:
> > >
> > > 1.  Has anyone come across this problem and researched into the
> > > magnitude of it?  Are there few or many motherboards out
> > there which are
> > > not compliant to the rev 2.2 spec, paragraph 4.3.3 --
> > requiring a pullup
> > > on TMS and TDI?
> >
> > I've seen a lot of variation on this, ranging from incorrect
> > pull-up/down to
> > no resistors at all.
> > >
> > > 2.  Are most PCI expansion cards designed without using the
> > JTAG pins of
> > > the PCI connector, hence most cards operate fine in these
> > non-compliant
> > > motherboards?
> >
> > At least to my experience. I've opted for bringing JTAG out
> > to a separate
> > connector in my designs, leaving the PCI JTAG as is (i.e.
> > connecting TDI to
> > TDO). This makes my JTAG chain independent of whatever the
> > motherboard and
> > other expansion cards are doing. The drawback is the need for
> > a separate
> > test connector and plugging into this during production test.
> >
> > Regards,
> > - Olaf
> >