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From: Oscar on 7 Dec 2008 07:11
On Dec 6, 9:46 am, "freesp...(a)gmail.com" <freesp...(a)gmail.com> wrote:
> On Dec 6, 8:27 pm, Glen Herrmannsfeldt <g...(a)ugcs.caltech.edu> wrote:> freesp...(a)gmail.com wrote:
>
> > (snip)
>
> > > I get the following log:
> > > Found Device.  IDCODE:  f5046093
> > > Found Device.  IDCODE:  21c2e093
> > > Found Device.  IDCODE:  invalid
> > > Found Device.  IDCODE:  invalid
> > > Found Device.  IDCODE:  invalid
>
> > I don't have this board so I might be just guessing,
> > but is there any reason that Xilinx software should recognize
> > non-Xilinx devices?
>
> Are you referring to IDs f5046093 and 21c2e093? Those appear to be
> Xilinx devices. I don't expect Xilinx to recognise non-Xilinx devices
> either, but that is not what is causing the invalid IDCODE messages:
> there are _only_ 2 devices on the board connected to the JTAG chain.
> My problem is there appears to be 29 other devices which aren't there,
> but is detected. This is causing Digilent's ExPort program to fail and
> thus preventing me from doing anything with the Nexys2.

Its almost like something is broken in the JTAG interface.
IIRC, this can happen if the host fails to find the end of the IDCODE
register when doing an initialization scan.
It looks like it reads in an extra 29 devices (likely all 1's) and
then stops because of a software 'timeout' (a neat 31 devices in an
array); it then cant find the device description files for the
spurious 29, and tells you that. I seem to remember that the way it's
supposed to detect the end of the scan chain is the lack of a '1' as a
first bit in the n+1 IDCODE out. If TDO is stuck high after the two
first devices, youd get something very much like what you sre seeing.

I'd try another JTAG scan tool to see what *that* reports.

Of course, I could also be dead wrong and its due to something
entirely different.

//Oscar
From: Sean Durkin on 7 Dec 2008 15:52
freespace(a)gmail.com wrote:
> there are _only_ 2 devices on the board connected to the JTAG chain.
> My problem is there appears to be 29 other devices which aren't there,
> but is detected.
Have you tried setting a slower cable speed? I've had things like this
happened when I used a too fast clock for JTAG. You can set the speed in
the iMPACT cable settings. The default is rather high, there have been
times when it wouldn't work unless I selected a slower speed.

HTH,
Sean
From: freespace on 8 Dec 2008 03:43
On Dec 7, 11:11 pm, Oscar <o.al...(a)gmail.com> wrote:
> On Dec 6, 9:46 am, "freesp...(a)gmail.com" <freesp...(a)gmail.com> wrote:
>
>
>
> > On Dec 6, 8:27 pm, Glen Herrmannsfeldt <g...(a)ugcs.caltech.edu> wrote:> freesp...(a)gmail.com wrote:
>
> > > (snip)
>
> > > > I get the following log:
> > > > Found Device.  IDCODE:  f5046093
> > > > Found Device.  IDCODE:  21c2e093
> > > > Found Device.  IDCODE:  invalid
> > > > Found Device.  IDCODE:  invalid
> > > > Found Device.  IDCODE:  invalid
>
> > > I don't have this board so I might be just guessing,
> > > but is there any reason that Xilinx software should recognize
> > > non-Xilinx devices?
>
> > Are you referring to IDs f5046093 and 21c2e093? Those appear to be
> > Xilinx devices. I don't expect Xilinx to recognise non-Xilinx devices
> > either, but that is not what is causing the invalid IDCODE messages:
> > there are _only_ 2 devices on the board connected to the JTAG chain.
> > My problem is there appears to be 29 other devices which aren't there,
> > but is detected. This is causing Digilent's ExPort program to fail and
> > thus preventing me from doing anything with the Nexys2.
>
> Its almost like something is broken in the JTAG interface.
> IIRC, this can happen if the host fails to find the end of the IDCODE
> register when doing an initialization scan.
> It looks like it reads in an extra 29 devices (likely all 1's) and
> then stops because of a software 'timeout' (a neat 31 devices in an
> array); it then cant find the device description files for the
> spurious 29, and tells you that. I seem to remember that the way it's
> supposed to detect the end of the scan chain is the lack of a '1' as a
> first bit in the n+1 IDCODE out. If TDO is stuck high after the two
> first devices, youd get something very much like what you sre seeing.
>
> I'd try another JTAG scan tool to see what *that* reports.
>
> Of course, I could also be dead wrong and its due to something
> entirely different.
>
> //Oscar

Interesting, I will keep it in mind Oscar, thank you.
From: freespace on 8 Dec 2008 03:44
On Dec 8, 7:52 am, Sean Durkin <news_MO...(a)tuxroot.de> wrote:
> freesp...(a)gmail.com wrote:
> > there are _only_ 2 devices on the board connected to the JTAG chain.
> > My problem is there appears to be 29 other devices which aren't there,
> > but is detected.
>
> Have you tried setting a slower cable speed? I've had things like this
> happened when I used a too fast clock for JTAG. You can set the speed in
> the iMPACT cable settings. The default is rather high, there have been
> times when it wouldn't work unless I selected a slower speed.
>
> HTH,
> Sean

I will ask the Digilent people. I have to use their ExPort program to
communicate with my Nexys2 since it uses some usb-jtag magic. I might
just by the Xilinx cable though if this continues to be a problem.

Thank you for your advice.
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