Zybo Z7 Secure Boot / PMod Ports

[schoechm]

Hello,

someone else here already found out that secure boot doesn't work with zybo z7-20 since it's production silicon:

The other poster got it to work by soldering a battery to the J15 port. I'd like to do that too but I'm a bit unsure how to go about it. In the manual for Zybo Z7 it says that the pins should only receive 3.3Vm but is it the same for the ports? And is there anything else specific I should take note about when selecting a battery? Does digilent produce special batteries for this kind of occasion? I'm also not sure which of the two entrances is the positive and which is the negative since I couldn't find it in the manual.

Pardon if these are stupid questions, I am a student and want to work with a securely booted system for my masters thesis, so I rather ask before I break something. Thanks in advance!

[JColvin]

Hi @schoechm,

I'm not sure where you're getting the 3.3V from (unless you're looking at FPGA pin J15, which is attached to a bank that is powered at 3.3V). Connector J15 for the battery should be 1.8V as per page 12 on the Zybo Z7 schematic, https://reference.digilentinc.com/_media/reference/programmable-logic/zybo-z7/zybo_z7_sch-public.pdf, where you can see VCCBATT_0 in the lower left of the IC19H.

To be clear, I also don't know for sure if adding a battery will work, as per Xilinx AR#47565, though perhaps this does not affect production devices based on AR#47916? I'm not certain. The folks on the Xilinx forum would be better able to provide a definitive answer on this aspect.

Let me know if you have any questions.

Thanks,
JColvin

[schoechm]

Thanks a lot, @JColvin the schematic helped me and I have tried to get BBRAM to work with battery attached now as described by the other poster. Unfortunately it did not work for me. Do you have any models of Zybo Z7 for which the secure boot function is supported? I am using the embedded vision bundle, and I already have an implementation I want to use for it, so I think it would be hard to switch to another board.

[JColvin]

Hi @schoechm,

Unfortunately no, Digilent does not have any support for secure booting for any of our products. If it is true that the secure boot does not work on production silicon, I can confidently say that all of our Zybo Z7 boards use production silicon as they were not developed until several years after Xilinx started making the production silicon.

Thanks,
JColvin