The problem of the board powering on and off

[zhanghan]

Hello，my board is designed by using chip MCIMX6Q5EYM10AD.i find that  When the board is powered up and down for about 200 times, the network port of the board will not  configured and work for several times.After many experiments, we find that this problem will no longer exist if  the software disables the uart debug port. The attached pictures are schematic diagrams of UART port and 100M network port. Besides，We have tested with an oscilloscope. When the board is powered off and on repeatedly, the RX signal of the UART will be interfered.  Although the uart function is forbidden to avoid this problem, the actual engineering application still needs this uart port for debugging.So can someone tell me what to do?

[igorpadykov]

Hi zhang

one can try to increase delay between on/off switching so board power circuits

were fully discharged. Also one can try to disconnect uart port from pc, as no

external voltages are allowed to be applied to unpowered processor according to

sect.4.2.1 Power-Up Sequence i.MX6DQ Datasheet

http://www.nxp.com/docs/en/data-sheet/IMX6DQCEC.pdf

Best regards
igor
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