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unknown devices in JTAG chain

Hi,

I designed a FPGA prototyping board with a Spartan XC2S200E and a XC18V02 PROM. To configure these devices I put a JTAG header on the board and routed it as described in the following Xilinx datasheet:

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At the software-side I use impact and the PC3 from Xilinx. When I start impact in boundary-scan mode, the PC3 will be detected (as PC3@200kHz) and the boundary-scan chain will be identified. But there's the problem: impact always detects 11 devices in the chain, but there are only two. And: Even though the two devices are original Xilinx parts, no ID codes were returned (or better: the returned codes don't match with Xilinx parts).

I checked the configuration connections and the power supply, but everything seems to be o.k. Has anybody of you an idea what the problem could be?

thanks, Kay

Reply to
Kay Schubert
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Kay,

I assume that you were using initialize chain to detect the devices. I also assume that you're using 6.1isp2 iMPACT to perform configuration. When iMPACT performs chain initialization, only TMS and TCK are toggled. Take a look at Xilinx soln 11857.

So if the chain isn't detected correct, you'll want to probe the TMS, TCK, and TDO pins of each device. (ie. are the pins connected correctly, anything shorted, etc...)

Other possible causes includes board SI, parallel port noise. You may want to contact the Xilinx hotline support for further help.

Regards, Wei

Kay Schubert wrote:

Reply to
Chen Wei Tseng

We have here a very strange thing.

Since the JTAG is a serial bus and since a jtag frame is complex (a big shifter register), you will have a JTAG chain working OK or KO, but not a result like your one.

Also, this trouble is coming from software, at 99%.

Make sure to use the last Xilinx software release and the last sp.

Otherway, on hardware and if you have access, cut the jtag chain and connect the JTAG signals to have only the FPGA on and in seconde time only the EEPROM on.

Laurent Gauch www.am> Kay,

Reply to
Amontec Team, Laurent Gauch

Hello,

I had the same problem with the same two chips. There were 13 devices on the my board. I used long leads (20 cm) from the PC3 to the board. After shortening both the parallel port cable (I used a 1.5 M 1:1 extension cable between the parallel port and the PC3 cable) and the leads to the board (to

5 cm) the problem was solved.

Mark

"Kay Schubert" schreef in bericht news:3fb3a20d$ snipped-for-privacy@news.uni-rostock.de...

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were

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Reply to
Mark van de Belt

Mark,

Thanks a lot for your help. I had the same problem: the leads to the board were to long (I made a PC3 on my own). So I shortened it (to about 10cm), took a parallel port extension cable and it works fine. Thank you and the other supporters once more...

Kay

"Mark van de Belt" schrieb im Newsbeitrag news: snipped-for-privacy@corp.supernews.com...

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Reply to
Anonymous

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