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Media Independent Interface Management (MIIM), or Management Data Input/Output (MDIO), is a serial bus protocol and is used for the IEEE 802.3 Ethernet standard and Media Independent Interface (MII). The MIIM/MDIO protocol is a simple two-wire serial interface with specific terminology to define the various devices on the bus. The device driving the MDIO bus is identified as the Station Management Entity (STA). The STA connects to the managed PHY to control the sub-layer of PHY referred to as MDIO Manageable Devices (MMD) and capture the status of the PHY devices the MDIO is managing. The Management Data Input/Output (MDIO) component can be used to read and write the PHY control register.
MDIO is a bidirectional shared bus structure that can provide a connection from the STA (initiator) up to 32 PHY (follower) devices, and each PHY can have its own 32 MMDs. All data is synchronously transmitted with respect to the Management Data Clock (MDC). The data line is a tri-state shared bus that is STA controlled for a write transaction or PHY handled during a read transaction. The MDIO interface clock (MDC) supports frequencies up to 2.5MHz. MDIO was originally defined in Clause 22 of IEEE 802.3. To meet the growing needs of 10 Gigabit Ethernet devices, clause 45 of the 802.3ae specification is introduced.
With the availability of the Cadence Verification IP for Ethernet, adopters can start working with these specifications immediately, ensuring compliance with the standard and achieving the fastest path to IP and SoC verification closure. The Ethernet verification IP provides a full-stack solution, including support to the PHY, MAC, and Management layers with a comprehensive coverage model and protocol checkers. Ethernet VIP covers all features required for full coverage verification closure. More details are available in the Ethernet Verification IP portfolio.