The MDIO interface is a simple, two-wire, serial interface, clock and data.
MDIO is used to connect a management entity and a managed PHY for the purposes of controlling the PHY and gathering status from the PHY.
The two lines include the MDC line [Management Data Clock], and the MDIO line [Management Data Input/Output].
The clock is point-to-point [driven by the MAC], while the data line is a bi-directional multi-drop interface.
The data line is Tri-state able and can drive 32 devices. [Tristate Definition]
The clock is defined with a period of 400nS, or a frequency of 2.5MHz. No data on the minimum or maximum pulse rise time.
Data is stable both 10nS before the rising edge of the clock and 10nS after the edge. Data is assumed to be valid at the rising edge.
The MDIO interface is found on a number of devices.
MDIO is also a part of the Ethernet Bus MII Interface. That link provides both the pin locations on the MDIO connector and of course the pin numbers.
Pin two is used to carry the data line [MDIO] and pin three is used to carry the clock line [MDC].
Note that this is a simple IC to IC interface so the ground connection is inferred and not counted as an interconnect.
Although MDIO is also a cable interface because the signal are run over a cable;
However the ground line is still not required to be referenced because ground is required by all the other lines on the cable as well.
So another interface standard references or uses this two wire interface, this topic coverage makes no reference to a mechanical connector.
In other words this would appear to be an electrical only interface, which does not define a connector.
Back to the 10/100 Base Ethernet page, or 1000 base Ethernet page for additional pinout tables and interface descriptions.
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