5 Replies Latest reply on May 2, 2018 9:38 AM by Carlos_A

    X540 SPD Pins

    rdebacker Green Belt

      I am using the X540-BT2 Ethernet controller in my design and I have a question regarding the SDP (software defined pins) pins.

      The X540 reference schematic does not tie these pins high or low.

      The X540 datasheet pin interface does not state that these pins have internal pull-ups or pull-downs.  There is a Note 1 that states these pins should have external Pup/Pdn's.

      In section 4.4.3 of the datasheet there is a statement that SDP0_1 and SDP1_1 have weak internal pull-down resistors.

      The I350 schematic checklist states that the if the SDP pins are not used they can be left disconnected.

       

      Do the SDP pins need to be connected to external pull-ups or pull-downs?

      The SDP Control Register (Datasheet 6.4.6.4) in the NVM is configured as 0x0000 for LAN0 and 0x0400 for LAN1.  Generic software controlled I/O.  All SDP pins inputs except SDP1_2.