JTAG not working with ZedBoard+FMC Ethernet card

Question

Hi,

I'm trying to use a ZedBoard with an Avnet FMC Ethernet card (https://www.avnet.com/shop/us/products/avnet-engineering-services/aes-fmc-netw1-g-3074457345635205181/ ), using the on-board Digilent USB-JTAG device. When the FMC card is connected, the JTAG chain seems to be broken - the Digilent target appears in Vivado Hardware Manager, but with no devices detected. When the FMC card is disconnected, everything works as it should.

ZedBoard Jumper settings:

JP7, JP8, JP9, JP10, JP11 - all connected to GND to select JTAG configuration.
J18 - 2V5 (correct for this FMC card)

All power supplies (3V3, 12V, 5V and VADJ) look good with the FMC connected.

I am using Vivado 2020.1.

Any ideas what could be going on? My guess is that this has something to do with the FMC card JTAG chain switch, but I can't see any reason this wouldn't work from the schematics.

Thank you,

Saajan

saajanchana_cc · Accepted Answer

Figured it out: it was nothing to do with the JTAG chain, the issue is that the FMC card is pulling the Zynq's power-on-reset low as per this PCB errata: https://www.avnet.com/opasdata/d120001/medias/docus/198/Network_FMC_Errata_200213.pdf . Even though the date code of my PCB (2019) is outside the range covered by the errata, it still seems to be a problem - removing Q1 allows the Zynq POR to go high.

JTAG not working with ZedBoard+FMC Ethernet card

Top Replies