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DP83867IS: speed selection

K.Yaita
Guru 29720 points

Part Number: DP83867IS

Hi Team,

I found SPEED SELECTION LSB/MSB in Basic Mode Control Register (BMCR) as the following.




Does it correspond to the following SPEED_SEL in Strap Configuration?



I wonder why only two mode(10/100/1000 or 100/1000) are prepared in strap configuration while 10 or 100 or 1000 can be selected in Basic Mode Control Register.
I don't have a detailed knowledge about ethernet, so your advice would be appreciated.

Best Regards,
Yaita / Japan disty

  • 0
    TI__Mastermind 23675 points
    Hi Yaita,

    Generally a customer that purchases a 1G capable PHY does not have interest in 10Mbps operation.
    Also, most industrial systems use 100Mbps speeds, with a few moving to 1G. This is why we allow the customer to strap in hardware to those two modes.
    To cover more modes would mean more pins to strap. This is not usually desired because it increases BOM size.
    Bit[13] and Bit[6] can be overridden and any type of forced mode can be implemented.
    Also, using the Auto-Negotiation field registers, advertisement of speed and duplex capability can be changed.

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    Guru 29720 points

    Hi Ross-san,

    Thank you for your support.
    I found datasheet is updated "SPEED_SEL strap bit name to ANEG_SEL" as the following.


    http://www.ti.com/lit/ds/symlink/dp83867is.pdf


    How to configure speed selection under strap configuration when auto-negotiation is disabled?
    Should we configure it by BMCR 13bit (SPEED SELECTION LSB) and 6bit (SPEED SELECTION MSB) because it seems speed selection can't be configured under strap configuration?

    Best Regards,
    Yaita

  • 0 in reply to K.Yaita
    TI__Mastermind 23675 points
    Hi Yaita,

    To configure the PHY for forced speed and duplex operation, please do the following:

    For 10BASE-T Full Duplex
    Set register 0x0 to value 0x0100

    For 10BASE-T Half Duplex
    Set register 0x0 to value 0x0

    For 100BASE-TX Full Duplex
    Set register 0x0 to value 0x2100

    For 100BASE-TX Half Duplex
    Set register 0x0 to value 0x2000

    For 1000BASE-T Full Duplex
    Set register 0x0 to value 0x0140

    For 1000BASE-T Half Duplex
    Set register 0x0 to value 0x0040

    Kind regards,
    Ross
  • 0 in reply to Ross Pimentel
    Guru 29720 points

    Hi Ross-san,

    Thank you for your reply.
    I understood it is possible to configure the PHY for forced speed and duplex operation by BMCR (Basic Mode Control Register).

    I believe it is impossible to configure the PHY for forced speed and duplex operation by strap configuration only.
    Is my understanding correct?

    Best Regards,
    Yaita