Genesys ZU 3EG technical issue with JTAG programming

[Kvass]

The JTAG cable is not being read at all when anything is connected to the FMC-LPC connector.

 

I have a new Genesys-ZU 3EG board which I am programming with Vitis. I am using the JTAG HS1 adapter to load my program into the board. This works when nothing else is connected to the board.

For my project, I connect another board to the FMC connector. I am using this board. When the FMC card is connected, my PC stops recognizing the JTAG connection. The connection is invisible to both Vitis and Vivado. I have nothing else connected to the Genesys board nor to the FMC adapter. 

Any insight would be appreciated,

-Kvass

 

edit: all LEDs that were on previously light up as normal, i.e. main and aux power LEDs are on, the "init" LED is on as well. My jumper on JP3 is connected to the JTAG pins as well

Edited June 22, 2021 by Kvass

[JColvin]

Hi @Kvass,

I'll have to look into this some more. I have a vague recollection about there being something weird about FMC JTAG connectivity, but I don't recall the details well enough at the moment to provide any useful detail.

Thanks,
JColvin

[zygot]

7 hours ago, Kvass said:

The JTAG cable is not being read at all when anything is connected to the FMC-LPC connector.

Usually, the JTAG chain runs through the FMC connector. Usually there's a way to bypass the FMC connector JTAG circuit so that it doesn't interfere with FPGA configuration. You only need to use the JTAG chain on a daughter card if there's something on it that you want to configure through JTAG.

One more thing to learn about when connecting add-on boards to your FPGA platform.

Edited June 23, 2021 by zygot

[Kvass]

Thanks for the responses. I did some digging, and yea, @zygot is right. The JTAG is read after the FMC connector, so is FMC_PRSNTN_M2C is held low, then the FPGA will never get to reading the onboard JTAG port. Somewhat complicates things, but I can work around this information now. 

 

[elodg]

FMC modules are inserted in series into the JTAG chain. FMC modules must make sure to insert a device there or loop TDI back to TDO if JTAG is not used. 

According to the schematic jtag signals go to a header: 
https://www.xilinx.com/support/documentation/boards_and_kits/xtp078.pdf

Just short the TDI and TDO pins on the module with a jumper.