10-20-2014 08:33 AM
I'm attempting to hook up one ZC706 board to another to test interfaces while I wait for my real boards to show up. I can program each ZC706 without problems, but as soon as I hook up them together via FMC-FMC cable to the LPC connectors, the Hardware Manager no longer finds any target devices. I'm using Vivado 2014.2.
From previous posts, I know that the U31/U32 JTAG bypass switches route the TDI/TDO though the connector, and presumably out to the other board. Perhaps there is some sort of contention when this happens. When I get my real board, I can route TDO to TDI which will (hopefully) solve the problem.
But for now, has anyone tried this with two ZC706 boards and found a solution to this problem?
10-20-2014 10:45 AM
It is going to depend on what the FMC-to-FMC cable does with the PRSNT_M2C_B and TCK/TMS/TDI/TDO connections.
If the TCK and TMS pins aren't no connects in the cable it will create contention and/or signal integrity problems.
If the PRSNT_M2C_B is grounded in the cable and TDI is not looped back to TDO at each connector then the chain will be broken.
10-20-2014 12:12 PM
Thanks for your response. The FMC-FMC cable is the one Xilinx recommends (Samtec 153151 custom flex jumper). I haven't been able to find any information other than it doesn't connect the power pins, so I assume it connects all others.
To summarize what I think is the issue, I'm going to call the ZC706 boards A and B:
What I need is to be able to bypass the LPC, force a loopback of TDI to TDO on a ZC706 board, or effectively turn off the JTAG in one of the boards. I'd really prefer to bypass the LPC.
I'm hoping I'm not only one who has tried using this Xilinx-recommended jumper to tie together two boards. Do you have any ideas as to a workaround?
10-20-2014 06:32 PM
I wasn't aware that Xilinx made any recommendations for this cable. Can you point me to where this recommendation is made?
10-21-2014 04:20 AM
It's down near the bottom: FMC-to-FMC cable. There are several flavors of it, including ones meant to link boards to mezzanine cards, but the one I have links LPC to LPC or HPC to HPC.
05-11-2016 05:37 PM