Other Parts Discussed in Thread: AM4377
Hello,
I use the DP83848K and a AM4377 on a board and have some strange behaviour on some of the boards.
I posted to the processor forum some time ago but didn't really get a solution: e2e.ti.com/.../am4377-qspi-flash-for-am4377-uniflash-cli
My main question is what happens with the TX_EN and TXD_1 to TXD_3 signals on a powerup?
The pins should be just input pins according to the datasheet but on my hardware these pins are driving 3.3V.
These signals are also used for the bootstrap configuration of the AM4377 which is why they are driven with a transceiver when the processor is booting.
The following is a measurement a powerup:
C1: PORz
C2: 3V3
C3: ECAT0_TXD0
C4: PHY_RESETn
The ECAT0_TXD0 signal should be 0V from the bootstrap config but as soon as the PHY is powered it goes to around 2.5 V and when the output of the transceiver (which tries to pull it low) is disabled it goes to 3.3V.
When i don't power the DP83848K at all (no voltage at Pin 1,18, 26) it works as intended and the TXD0 isn't pulled up to 3.3 V.
Do you have any suggestions what the problem is or why it's behaving like this?
Thanks very much and best regards,
Timo
