FMC-CE Breaks JTAG Chain

[sdm]

I've got the FMC-CE board plugged into a ZC706, and when I try to load open the Hardware Manager in Vivado, it finds my HW target, but there are no devices found.  After a little digging I found that there is an FMC design rule that if you don't use the JTAG chain you need to tie the FMC TDI pin to the TDO pin.  Looking at the schematic, this isn't done on the FMC-CE board.  Both of these FMC pins (D30, D31) are disconnected.  What's the best way to work around this to enable JTAG debug when this board is installed?

[jpeyron]

Hi @sdm,

I reached out to one of our design engineers about this thread and they responded that you are correct the FMC-CE does not follow the FMC specification and connect the TDI pin to the TDO pin. However, the FMC-CE also doesn’t connect the PRSNT_M2C_L to ground like it should. Therefore the ZC706 should not detect the FMC-CE and should be connecting “FMC_HPC_TDO_FMC_LPC_TDI” to “FMC_LPC_TDO_FPGA_TDI” through U31 (page 28 of ZC706 schematic), which is effectively the same thing as the FMC-CE connecting TDI to TDO. Since present is pulled high on the ZC706 and is floating on the FMC-CE they don’t know why it’s not working.

thank you,

Jon

[sdm]

Agreed.  Thanks for that explanation.  I was using a newly configured carrier card (ZC706) and this new FMC card together, and assumed it was the FMC card causing the JTAG issues based on what I saw with TDI/TDO on the scematic.  It turns out that the ZC706 JTAG configuration switch (SW4) was configured incorrectly.

Thanks!

[jpeyron]

Hi @sdm,

Glad to hear you were able to find the issue. Thank you for sharing what it was.

Cheers,

Jon