I’m looking at ignoring the RSTN signal if it is not really required to simplify some interfaces so the question is, if I do not use this pin and rely on POR then does the W5500 still respond to software reset via SPI? Is this reliable?
W5500 have no POR.
So, W5500’s RESET could be controlled by your POR ic/circuit or MCU’s GPIO.
W5500’s RESET signal could not be floated.
Software reset by SPI is available after hardware reset is safely completed.
W5500 Reset needs timming… (for more detail, refer to datasheets)
Low : 500us
High : 1ms
That’s okay, but page 44 of the datasheet PHY configuration infers that this is the case when it says
"When W5500 is reset by POR or RSTn PIN," . So maybe that needs to be changed to “When W5500 is reset by RSTn PIN”.
Also in the same section “After POR or RSTn reset,” needs to be fixed.
So that line can’t be floated, is that right? Yet section 5.3 states
"RPU – Pull-up Resistor – SCSn, RSTn, PMODE[2:0] – 62 – 77 – 112 Kohm"
RSTn , SCS, PMODE signals are internally pulled-up resister.
It maybe floated. But RSTn need to be controlled by other logics as POR, push button and GPIO.
Anyway, Datasheet will be updated.