I'm a test engineer for a PCBA contract manufacturer working on a failure for a Defense customer product employing the Xilinx Stratix IV GX FPGA.
The device is returning the wrong IDCODE during Boundary Scan, and it fails to program. We have reviewed the assembly for workmanship issues, and when none were found, we replaced the VERY expensive device, only to have it repeat the failure.
We seem to have so little visibility to this device and cannot tell what the problem might be. HOPING there may be some kind folks with some suggestions as to how we can drill down to the root cause of this failure?
The measured data is flipping polarity on bits 15:19, which is odd given it does not align to a byte boundary?
Apologies for my late reply here ('was' struggling to recover my pw).
We were unable to program the FPGA as it didn't appear to be getting far enough into boot to accept the programming. Additionally, after speaking a little more with the technician, he indicated the failure mode was different after replacing the IC. This now makes me believe we did not achieve a good "collapse" of the BGA when it was attached. The assembly went through the removal, re-ball, and reinstall process and is able to pass Boundary Scan now.
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