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Error Scanning JTAG Chain

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13 posts / 0 new
bkeitch's picture
bkeitch
Junior(0)
Error Scanning JTAG Chain

If I connect the Zedboard via JTAG I get the following error in XMD:

XMD% connect arm hw
Error:No devices detected while scanning the JTAG chain
ERROR: Failed to Scan JTAG Chain
Unknown Error

I followed the instructions in:

ZedBoard Configuration and Booting Guide V 1.1 Aug 2012

setting all the MIO jumpers to ground.

I have also tried a Xlinx PLatform Cable and get the same error.

I am running Xilinx 14.3 (Windows 7/64) which works with an ML507 board. The board's JTAG device is installed (Driver: FTDI v2.8.24.0) and this is detected by Adept as device "Zed":

===== Digilent Adept Rev 2.2.0 =====
Loading board information...
Warning: Could not find specific board information
Initializing Scan Chain...
Default information loaded.
Initialization Complete.
It then says "No Devices identified"

This would suggest both JTAG programmers and software are working, but the problem is on the board with the JTAG chain. Please help. Thanks.

bkeitch's picture
bkeitch
Junior(0)
Fixed! Turns out this is a

Fixed! Turns out this is a problem due to the FMC break out board being connected. If the HW-FMC-105-DEBUG board is not connected, everything works fine! Would anyone like to explain to me why this is?

zedhed's picture
zedhed
Moderator(25)
RE: Error Scanning JTAG Chain

Hi bkeitch,

After looking at this a little bit closer, I think I understand what is going on here.  The ZedBoard JTAG chain was designed to allow the FMC JTAG chain to be inserted into the scan chain which would allow for things like Boundary Scan Test or In-Circuit Programming of FMC devices.  When an FMC is attached to ZedBoard, the Carrier (in this case ZedBoard) FMC present signal FMC-PRSNT gets pulled down by the module.  This in turn enables the buffers in IC1 to connect the ZedBoard JTAG signals to their FMX-x equivalents.  Likewise, IC2 is a selector IC which connects the TDI-USB signal to FMC-TDO instead of the default TDO-FPGA signal.  

So unless the chain gets completed on the FMC by connecting additional IC JTAG TAPs, when an FMC is connected, there is no longer a solid path for TDO-FPGA to reach the ZedBoard J15 connector OR the USB-JTAG circuit.  This would explain why you see interference with the Platform Cable when connecting your FMC-XM105 card.

On some of the FMC cards, there is a series resistor before FMC-PRSNT reaches GND which would give one option for disabling FMC-PRSNT and restoring the chain.  However, that is not the case with the FMC-XM105 since FMC-PRSNT is tied directly to GND. 

Looking closer, it does appear that the FMC JTAG signals reach the J5 connector on FMC-XM105.  I do not have an FMC-XM105 to try this on here, but it seems like you should be able to put a jumper across pins 6 and 7 on J5 and restore a signal path to the Carrier board to complete the JTAG chain.

That might not be the ultimate solution, but I don’t think that you would damage anything by trying this either.  If it does solve the problem, could you please let us know?

 

Regards,

-Kevin

alexktdla's picture
alexktdla
Junior(0)
jumper works

installing a jumper on J5 between pins 6 and 7 fixes the JTAG

bkeitch's picture
bkeitch
Junior(0)
Kevin,

Kevin,

Thanks so much for explaining that and taking the time to look into it. Yes, the jumped does work. I think this will be useful for everyone using the FMC-105 board with the Zedboard.

Ben

mukesh's picture
mukesh
Junior(0)
On Debug card J5 ( TDO ,TDI)

On Debug card J5 ( TDO ,TDI) make it short from sdk its working.

ravi_1989's picture
ravi_1989
Junior(0)
Short TDO and TDI

Hello Mukesh
I want to know that how to short (TDO and TDI) from SDK.
 
Please help me out.

mukesh's picture
mukesh
Junior(0)
FMC module J5

TDO ,TDI make it short it will work

dannna's picture
dannna
Junior(0)
JTAG problem

Hi, I's also using Zedboard with FMC105. I connected a jumper between FMC-TDI and FMC-TDO and JTAG chain worked fine.
Few days later suddenly I get an error while JTAG cable scans :"There are too many unknown deviced being detected". I checked connections on board and everything seems fine.. What can I do?

Thanks,
Danna

TroutChaser's picture
TroutChaser
Moderator(18)
Hello Danna,

Hello Danna,
 
Sounds like a physical connection issue. I would try removing the FMC board first and make sure the JTAG cable scans OK. Then I would add the FMC board back and check that the jumper you are using is really making a good connection between the TDI and TDO signals.
 
-Gary

dannna's picture
dannna
Junior(0)
Thanks Gary,

Thanks Gary,

JTAG chain works good without FMC 105. I also checked the jumper and the PRSNT signal with a fluke. I also measures resistance between FMC and Zedboard grounds, it was less then 1 ohm. I also measured Voltages and it seems fine..
What else can I check?

Thanks,

TroutChaser's picture
TroutChaser
Moderator(18)
 

 
Danna,
 
The only other thing I can suggest is to check the IC2 circuit, pictured above, to see if there is a problem on your board with that circuit.
 
-Gary

ravi_1989's picture
ravi_1989
Junior(0)
Hello Mukesh and other fellow

Hello Mukesh and other fellow
I want to know how to short TDO and TDI from SDK.
 
Thank you.
 
Looking forward for your response.