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AM5K2E02: Does the GbE subsystem support 802.3Z (1000BASE-SX Multi-mode Fibre) SFP

aaron glover
Prodigy 10 points
Part Number: AM5K2E02

I have an application where I would like to use SFPs to enable the choice of either copper Ethernet 10/100/1000BASE-T or fibre Ethernet 1000BASE-SX. The majority of copper SFPs I have seen require an SGMII interface running at 1.25Gbps where there is a PHY within the SFP which adjust the data rate to match the network by padding the SGMII link. However for fibre SFPs running 1000BASE-SX I dont believe there is a PHY - just a bidirectional electron to photon conversion and therefore the MAC needs to support 1000BASE-X.

Does the AM5K2E02 support SGMII and 1000BASE-X (802.3z) on its Gigabit (or 10GbE) Ethernet Subsystem for use with 1Gbps SFPs (to SFF-8074I)?

Or perhaps these two variants of SFP can be supported by the SRIO SERDES?

  • 0
    TI__Guru**** 161600 points
    Hi,

    I've notified the factory team. Their feedback will be posted here.

    Best Regards,
    Yordan
  • 0 in reply to Yordan Kovachev
    TI__Mastermind 46460 points

    Aaron,

    The IEEE802.3 specification defines Ethernet MAC and PHY functionality. This specification is structured so that MAC functionality remains constant while physical layer dependent functions can be changed depending on the medium used.  1000BASE-SX is a SERDES interface used to connect the Physical Medium Attachment (PMA) with the Physical Medium Dependent (PMD) fiber optic transceivers within the PHY functional block.  SGMII is a MAC-to-PHY interface.  From an electrical point of view, the SGMII interface is very similar to the SERDES interface.  Both use 8B/10B encoding over a SERDES link running at 1.25GBaud for a raw data throughput of 1.0Gbps.  However, as stated previously, they exist at distinctly different locations in the Ethernet stack and are not interchangeable.  These interfaces have different requirements which result in different features being supported.  For instance, SGMII needs to support auto-negotiation so that it can inform the MAC device that the attached PHY has negotiated full or half duplex, flow control and status information.  Alternately, 1000BASE-SX supports 1.0Gbps without any negotiation.

    The SGMII port on the AM66K2Exx devices can be configured for SGMII slave (i.e. standard MAC mode), SGMII master (i.e. PHY mode used for MAC-to-MAC connections) and Forced. If negotiation communication is disabled and the settings for speed, duplex and flow-control are all forced to the same setting at both ends of the link, then the SGMII port operates equivalent to the SERDES interface in 1000BASE-SX.

    I went through the details above because we wanted you to understand that an SGMII port is not compatible with 1000BASE-SX and why. We also then wanted you to understand that the electrical interface is identical when used in a Forced configuration and that with proper configuration, the SGMII port on AM66K2Exx devices can be connected to a fiber optic PMD and made to operate.  However, as noted, this implementation is not compliant to the IEEE 802.3 defined architecture.

    Tom