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V62/12615-01XE-R Datasheet(PDF) 41 Page - Texas Instruments |
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V62/12615-01XE-R Datasheet(HTML) 41 Page - Texas Instruments |
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41 / 97 page ![]() MDC MDIO (STA) Idle Start Opcode (Write) PHY Address (PHYAD = 0Ch) Register Address (00h = BMCR) TA Register Data Idle z z 0 1 0 1 0 1 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 z z MDC MDIO (STA) Idle Start Opcode (Read) PHY Address (PHYAD = 0Ch) Register Address (00h = BMCR) TA Register Data z MDIO (PHY) z z Idle z z z z 0 1 0 1 0 1 1 0 0 0 0 0 0 0 0 0 0 0 0 0 1 1 1 0 0 0 0 0 0 0 0 41 DP83848-EP www.ti.com SLLSEC6E – SEPTEMBER 2012 – REVISED JUNE 2019 Submit Documentation Feedback Product Folder Links: DP83848-EP Detailed Description Copyright © 2012–2019, Texas Instruments Incorporated The Start code is indicated by a <01> pattern. This assures the MDIO line transitions from the default idle line state. Turnaround is defined as an idle bit time inserted between the Register Address field and the Data field. To avoid contention during a read transaction, no device shall actively drive the MDIO signal during the first bit of Turnaround. The addressed DP83848-EP drives the MDIO with a zero for the second bit of turnaround and follows this with the required data. Figure 5-2 shows the timing relationship between MDC and the MDIO as driven/received by the Station (STA) and the DP83848-EP (PHY) for a typical register read access. For write transactions, the station management entity writes data to the addressed DP83848-EP thus eliminating the requirement for MDIO Turnaround. The Turnaround time is filled by the management entity by inserting <10>. Figure 5-3 shows the timing relationship for a typical MII register write access. Figure 5-2. Typical MDC/MDIO Read Operation Figure 5-3. Typical MDC/MDIO Write Operation 5.4.3.3 Serial Management Preamble Suppression The DP83848-EP supports a Preamble Suppression mode as indicated by a one in bit 6 of the Basic Mode Status Register (BMSR, address 01h.) If the station management entity (i.e. MAC or other management controller) determines that all PHYs in the system support Preamble Suppression by returning a one in this bit, then the station management entity need not generate preamble for each management transaction. The DP83848-EP requires a single initialization sequence of 32 bits of preamble following hardware/software reset. This requirement is generally met by the mandatory pullup resistor on MDIO in conjunction with a continuous MDC, or the management access made to determine whether Preamble Suppression is supported. While the DP83848-EP requires an initial preamble sequence of 32 bits for management initialization, it does not require a full 32-bit sequence between each subsequent transaction. A minimum of one idle bit between management transactions is required as specified in the IEEE 802.3u specification. |
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