A new ST code (00) is defined to identify Clause 45 data frames. In order to accomplish this, several changes were made in the composition of the data frame. Secondly, by creating a address frame, the register address space is increased from 5 bits to 16 bits, which allows an STA to access 65,536 different registers. The benefits of adding this two cycle access are that Clause 45 is backwards compatible with Clause 22, allowing devices to interoperate with each other. ![]() A second frame is then sent to perform the read or write. First an address frame is sent to specify the MMD and register. In Clauses 22, a single frame specified both the address and the data to read or write. The primary change in Clause 45 is how the registers are accessed. Turnaround time to change bus ownership from STA to MMD if requiredĭriven by MMD during read-increment-address Clause 22Ĭlause 22 defines the MDIO communication basic frame format (figure 13) which is composed of the following elements: MDC is specified to have a frequency of up to 2.5 MHz. The STA initiates all communication in MDIO and is responsible for driving the clock on MDC. The target devices that are being managed by the MDC are referred to as MDIO Manageable Devices (MMD). The device driving the MDIO bus is identified as the Station Management Entity (STA). MDIO has specific terminology to define the various devices on the bus. The MDIO bus has two signals: Management Data Clock (MDC) and Managment Data Input/Ouput (MDIO). Additional OP-code and ST-code for Indirect Address register access for 10 Gigabit Ethernet.Ability to access 65,536 registers in 32 different devices on 32 different ports.To meet the needs the expanding needs of 10-Gigabit Ethernet devices, Clause 45 of the 802.3ae specification provided the following additions to MDIO: These registers provide status and control information such as: link status, speed ability and selection, power down for low power consumption, duplex mode (full or half), auto-negotiation, fault signaling, and loopback. In the original specification, a single MDIO interface is able to access up to 32 registers in 32 different PHY devices. MDIO was originally defined in Clause 22 of IEEE RFC802.3. The management of these PHYs is based on the access and modification of their various registers. See sub_mdio_xfer_ex.Management Data Input/Output, or MDIO, is a 2-wire serial bus that is used to manage PHYs or physical layer devices in media access controllers (MACs) in Gigabit Ethernet equipment. To access MDIO1 channel use sub_mdio_xfer_ex function with channel=1.īeginnig from FW version 0.3.2 and library version 0.1.12.24, SUB-20 supports CFP MSA compatible transactions at 4MHz MDC frequency. SUB-20 supports both MDIO frame formats defined in IEEE 802.3 Clause 22 and Clause 45.īeginning from FW version 0.2.8 and library version 0.1.12.18, additional MDIO1 channel is available on SPI header ( see SPI Header ). ![]() Status information is driven by the PHY synchronously with respect to MDC and is sampled synchronously by the SUB-20. Control information is driven by the SUB-20 synchronously with respect to MDC and is sampled synchronously by the PHY. ![]() MDIO is a bidirectional signal between PHY and the SUB-20 It is used to transfer control information and status between the PHY and the SUB-20. MDC is sourced by SUB-20 to the PHY as the timing reference for transfer of information on the MDIO signal. Where a PHY, or grouping of PHY's, is an individually manageable entity, known as an MDIO Manageable Device (MMD). It is two signal based interface between Station Management (SUB-20 in our case) and a Physical Layer device (PHY). MDIO is a Management Data Input/Output Interface defined in IEEE 802.3 Clause 22 and extended in Clause 45.
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