Xilinx IMPACT Problem... detects 101 unknown devices

Sounds like your JTAG chain is screwed up.

-a

please tell me what should i do now to set it right? should i read something or should i check for something? why does it detect so many devices when i have only one FPGA in there? ...thanks

Scanning the JTAG chain for devices is done by reseting the TAP controllers which loads the devices IDCODE into the TAP output register and then shifting the register out and waiting until you get a set of 32 ones (zeros??) indicating the end of the chain.

The most likely cause is that you have connected the TDO cable pin to something other than the TDO pin of the last device in the chain that is generating bad data back to the cable.

Ed

Subhasri krishnan:

I've had problems with too many detected devices when the cable frequency was too high. You can change it in the cable setup settings. If you use a Parallel Cable IV and it is properly detected, iMPACT usually sets it to a default of 5MHz. Try lowering the frequency and see if it gets any better.

cu, Sean

I have had some problems similar to that in that I would get a strange number of devices rather than the six I have on the board. The Xilinx people pointed out the signal integrity issues I designed. Mostly the TCK line was the culprit. How is your TCK line routed? Is there a series resistance? Or perhaps you put an end Thevenin termination at the end? How long are the lines?

My ISE7.1 says parallel cable drivers installed, but refuses to recognize my old cable III and tries using anon-existent multilink. Seems to be reading Prom & Virtex Id's, but can't start them after program. How do I get IMPACT to accept a Cable III ?

I've seen this happen with a dodgy JTAG cable.

Jeremy

some parallel cable III have the wrong logic to use with low voltage parts... mine wont work below 3.3V.. what is your Jtag?

Simon

my old cable III and tries using anon-existent multilink. Seems to be reading Prom & Virtex Id's, but can't start them after program. How do I get IMPACT to accept a Cable III ?

Thanks for the input everyone.The "101 device" problem has been fixed. It turned out that the voltage on the download cable is too low. should be 2.8v and above, the design was only 2.5v. Now it is 3.3v.

But there is the error of "impact 583:the idcode read from device does not match idcode in bsdl file". We think that the TDO's voltage is too low (3.3v), while the TDO requires TTL > 4v. We are going to try this tomorrow. But can anyone here think of another reason?

Thanks

Recheck to see if the "Correct" BSDL file is associated with the device in question. I've seen after impact gets confused, one has to assign the BSDL file to the part, exit impact and restart. Consult Xilinx answer records for more information.

-Newman

Sorry, had been on conference last week. Parallel port is on a laptop, JTAG is

3.3v powered, connects to CESYS.com Xv2ddr module (Xc2v1000-456-5 plus xc18v04 prom) all run on 3.3. IMPACT gives me only a (nonexistent) multilink as choice, par3/4 are grayed out. Installation record says parallel cables drivers installed, no further details. IMPACT doesn#t recognize cable II in config-detect. Somethings wrong or missing in setup. How do I postinstall old cables ? no choice in installing from cd. Ciao, klaus

I've used a parallel cable 3 (home built) on Spartan 2/e's.. but they don't work above that.. defiantly not on Spartan 3's .. voltages are all wrong.

I would strongly recommend you don't be so cheap and buy the USB downloader!

JTAG is 3.3v powered, connects to CESYS.com Xv2ddr module (Xc2v1000-456-5 plus xc18v04 prom) all run on 3.3. IMPACT gives me only a (nonexistent) multilink as choice, par3/4 are grayed out. Installation record says parallel cables drivers installed, no further details. IMPACT doesn#t recognize cable II in config-detect. Somethings wrong or missing in setup. How do I postinstall old cables ? no choice in installing from cd. Ciao, klaus