RE: JTAG pins

[Lame Brooks-G14738 <Brooks_Lame-G14738@email.mot.com>]

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
>