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Introduction To Multi-Rate Compatibility Of 10G Copper SFP Modules Based On BCM84891L

Time: 2023-07-14
        This article introduces the rate compatibility of the host interface and twisted-pair (RJ45) interface for 10GbE copper SFP modules based on the Broadcom BCM84891L solution.
1. Host Interface
        The host interface of the BCM84891L-based 10GbE SFP module supports adaptive mode switching, compatible with 10G XFI, 5GBase-X, 2.5GBase-X, and SGMII modes. Its working mode is automatically adapted according to the switch port rate, with corresponding twisted-pair interface rate limitations and transmission distances as follows:
        • When the switch port is set to 10G
        The module’s host interface adapts to 10G XFI mode. At this time, the twisted-pair interface only supports the 10GBase-T 10G rate, with a maximum transmission distance of 80 meters over Cat 6A or higher-grade cables.
Block diagram of the BCM84891L 10GbE SFP module on a 10G switch port
Figure 1 Block Diagram of the BCM84891L 10GbE SFP Module on a 10G Switch Port
        • When the switch port is set to 5G
        The module’s host interface adapts to 5GBase-X mode. At this time, the twisted-pair interface only supports the 5GBase-T 5G rate, with a maximum transmission distance of 100 meters over Cat 5E or higher-grade cables.
Block diagram of BCM84891L 10GbE SFP module used on 5G switch port
Figure 2 Block Diagram of the BCM84891L 10GbE SFP Module on a 5G Switch Port
        • When the switch port is set to 2.5G
        The module’s host interface adapts to 2.5GBase-X mode. At this time, the twisted-pair interface only supports the 2.5GBase-T 2.5G rate, with a maximum transmission distance of 100 meters over Cat 5E or higher-grade cables.
Block diagram of BCM84891L 10GbE SFP module on 2.5G switch port
Figure 3 Block Diagram of the BCM84891L 10GbE SFP Module on a 2.5G Switch Port
        • When the switch port is set to 1G
        The module’s host interface adapts to SGMII mode. At this time, the twisted-pair interface only supports 10/100/1000Base-T rate auto-negotiation, with a maximum transmission distance of 100 meters over Cat 6A or higher-grade cables.
Block diagram of BCM84891L 10GbE SFP module on 1G switch port
Figure 4 Block Diagram of the BCM84891L 10GbE SFP Module on a 1G Switch Port
2. Twisted-Pair (RJ45) Interface
        The twisted-pair side (RJ45 connector) of the BCM84891L-based 10GbE SFP module supports interconnection with remote modules at six rates: 10/100/1000 Mbps, 2.5G/5G/10G.
        A key note: The rate of the twisted-pair interface must be consistent with the host interface rate, and the host interface rate is synchronized with the switch port rate. Therefore, the switch port rate determines the available interconnection rate of the twisted-pair interface. To switch the interconnection rate during use, you must first adjust the rate of the local switch port.
3. Flow Control
        For the BCM84891L solution, the 10GbE PHY operates at the same rate on both the host side and twisted-pair side. No internal rate conversion is required, so flow control is not needed.
        Moduletek’s 10GbE SFP copper modules based on the BCM84891L solution deliver stable performance at a competitive price. Welcome to purchase!
        Moduletek Limited is at your service.
        For further inquiries about the above content, please contact us at: sales@moduletek.com
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