Executive summary: - adding a pull-up to CE0 has no significant effect on NOR corruption - next: reset chip rework
The details ----------- This time, I also pulled up the CE0 (chip enable zero) line: http://downloads.qi-hardware.com/people/werner/m1/nor/d7/nor-ce0.jpg This is again a 4.7 kOhm resistor to 3.3 V. Soldered "wirelessly" directly to neighbouring pads. As expected, the results look familiar: http://downloads.qi-hardware.com/people/werner/m1/nor/d7/out.png NOR corruption still occurs and happens quite often. The observed frequency is a bit lower than before, but I think this is caused by having only a small number of samples. Had I given it a few more days, the results would probably look exactly like in the previous runs. Once again, I ran into an uncommanded locking of the first block, this time after, estimated, 6300-8500 cycles. The corruption pattern also looks familiar: 00000 ____________________ | 00000000 00010000 | d7/1376-corrupt.bin | 00000000 00000000 | d7/2892-corrupt.bin | 00000000 00010000 | d7/5633-corrupt.bin 0000c ________________11__ | 00000100 01000000 | d7/6295-corrupt.bin 0003c ______________1111__ | _____0__ ________ | d7/6062-corrupt.bin 1/2 00082 ____________1_____1_ | _0__00__ 0_____00 | d7/1376-corrupt.bin 1/1 | _0__00__ 1_____00 | d7/6062-corrupt.bin 2/2 0008c ____________1___11__ | 00_00___ _0___000 | d7/5633-corrupt.bin 1/1 00410 _________1_____1____ | ________ _100____ | d7/1635-corrupt.bin 1/1 00480 _________1__1_______ | ________ 0_0_0___ | d7/329-corrupt.bin 1/1 007fe _________1111111111_ | ________ __0_____ | d7/3803-corrupt.bin 1/1 00800 ________1___________ | ________ ____0___ | d7/3473-corrupt.bin 1/1 00850 ________1____1_1____ | ________ 0_0_0___ | d7/3634-corrupt.bin 1/1 00fb0 ________11111_11____ | ________ _001____ | d7/2892-corrupt.bin 1/1 01100 _______1___1________ | ________ 0_0_____ | d7/6295-corrupt.bin 1/1 Conclusion ---------- The two pull-ups (WE# and CE0) Xilinx recommend in their manual don't have an effect on our NOR corruption, but they also don't cause any ill side-effects. In general, I think it still is a good idea to add the pull-ups in a future board revision. What's next ----------- After checking those two "low-hanging fruit" reworks, the path is now clear for the experiment that we hope will remove the root cause of all this for good: connecting the reset chip to the 5 V supply instead of the 3.3 V rail, and using a reset chip with a higher threshold voltage. I've already done the rework and a test is running now. - Werner _______________________________________________ http://lists.milkymist.org/listinfo.cgi/devel-milkymist.org IRC: #milkymist@Freenode
