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Bad Phy strap values captured on Nucleo144 boards

Question asked by Uwe Bonnes on Sep 2, 2016
Latest reply on Sep 5, 2016 by ForumSTM32.ForumSTM3
On one Nucleo-F746ZG and two NUCLEO-F767ZI boards, I have noticed that the captures strap values for Mode and Addr[0] often disaggree to the strapped values. The Phy LAN87xx requires the strap lines to be release at maximum 50 ns after NRST asserted. With NRST asserted on a running system, this requirement is probably not meet on the Nucleo144 boards.

I can resolve in two ways:
- Remove NRST <-> Phys RST Jumper SB 177 so that strap values only get captured with Power on reset with strap lines still in Hi-Z by the CPU so the resistor set strap value is not disturbed.
- Write Phy Register 18 lower byte to 0xe0 before giving a soft reset to the phy.