Virtex 4 USER1 ~ USER4 JTAG commands

Hello everyone,

I'm trying to use Virtex4 (Virtex4 LX25 Xilinx ML401 board) USER1 ~ USER4 JTAG commands from my software.

I have used my software to access such USER1, USER2 commands in previous generation FPGAs such as Virtex-II.

Virtex 4 uses different JTAG command bit patterns (10 bit long) and I changed the table so that JTAG commands to be issued have the correct JTAG command bit patterns.

Anyway, after spending hours and hours, I couldn't make it working. The JTAG command sequence seems correct as far as I see in the scope and HEX print out. Also, I can get the correct IDCODE using JTAG IDCODE command.

IDCODE = 10'b1111001001 USER1 = 10'b1111000010

I added probes to BSCAN module signals so that I could see the signals coming out from the BSCAN module. But I didn't see any signals coming out from the BSCAN module even I tried all USER1 ~ USER4 commands. (ex. sendIR(USER1) + readDR())

My question is "Does anybody try using the Virtex4 USERx JTAG command?"

If anybody have tried it, I definitely would like to hear that. I checked the Internet newsgroup as well as Xilinx support but so far, I cannot find any relevant info regarding to this.

Any info, any suggestions would be highly appreciated.

Best regards, Aki Niimura

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read the ERRATA !!!

V4 ES silicon only has USER1 command USER2,3,4 are not working at all.

Antti PS the USER1 seems to work as the XMD and ChipScope both can communicate over USER1

schrieb im Newsbeitrag news:

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Antti Lukats


Antti, you saved my day. I was actually using USER2 command and my Virtex-4 is an ES part.

These day so many thing I need to read and everybody is using ERRATA to justify the bugs they made (actually I do, too). But I should have been more careful about such.

Anyway, thank you for your prompt response.

Best regards, Aki Niimura

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Additional info: I found Xilinx Answer Record #20129 mentioning the problem in the Virtex 4 LX25 ES part.


In short, LX25's JTAG BSCAN block is broken (ES part). I painfully found that the JTAG Reset signal polarity was inverted!

Hope other people won't stumble on this problem like me.


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