SNLS505F July   2016  – June 2021 DP83822H , DP83822HF , DP83822I , DP83822IF


  1. Features
  2. Applications
  3. Description
  4. Revision History
  5. Device Comparison Table
  6. Pin Configuration and Functions
  7. Specifications
    1. 7.1  Absolute Maximum Ratings
    2. 7.2  ESD Ratings
    3. 7.3  Recommended Operating Conditions
    4. 7.4  Thermal Information
    5. 7.5  Electrical Characteristics
    6. 7.6  Timing Requirements, Power-Up Timing
    7. 7.7  Timing Requirements, Power-Up With Unstable XI Clock
    8. 7.8  Timing Requirements, Reset Timing
    9. 7.9  Timing Requirements, Serial Management Timing
    10. 7.10 Timing Requirements, 100 Mbps MII Transmit Timing
    11. 7.11 Timing Requirements, 100 Mbps MII Receive Timing
    12. 7.12 Timing Requirements, 10 Mbps MII Transmit Timing
    13. 7.13 Timing Requirements, 10 Mbps MII Receive Timing
    14. 7.14 Timing Requirements, RMII Transmit Timing
    15. 7.15 Timing Requirements, RMII Receive Timing
    16. 7.16 Timing Requirements, RGMII
    17. 7.17 Normal Link Pulse Timing
    18. 7.18 Auto-Negotiation Fast Link Pulse (FLP) Timing
    19. 7.19 10BASE-Te Jabber Timing
    20. 7.20 100BASE-TX Transmit Latency Timing
    21. 7.21 100BASE-TX Receive Latency Timing
    22. 7.22 Timing Diagrams
    23. 7.23 Typical Characteristics
  8. Detailed Description
    1. 8.1 Overview
    2. 8.2 Functional Block Diagram
    3. 8.3 Feature Description
      1. 8.3.1 Energy Efficient Ethernet
        1. EEE Overview
        2. EEE Negotiation
      2. 8.3.2 Wake-on-LAN Packet Detection
        1. Magic Packet Structure
        2. Magic Packet Example
        3. Wake-on-LAN Configuration and Status
      3. 8.3.3 Start of Frame Detect for IEEE 1588 Time Stamp
      4. 8.3.4 Clock Output
    4. 8.4 Device Functional Modes
      1. 8.4.1  MAC Interfaces
        1. Media Independent Interface (MII)
        2. Reduced Media Independent Interface (RMII)
        3. Reduced Gigabit Media Independent Interface (RGMII)
      2. 8.4.2  Serial Management Interface
        1. Extended Register Space Access
        2. Write Address Operation
        3. Read Address Operation
        4. Write (No Post Increment) Operation
        5. Read (No Post Increment) Operation
        6. Write (Post Increment) Operation
        7. Read (Post Increment) Operation
        8. Example Write Operation (No Post Increment)
        9. Example Read Operation (No Post Increment)
      3. 8.4.3  100BASE-TX
        1. 100BASE-TX Transmitter
          1. Code-Group Encoding and Injection
          2. Scrambler
          3. NRZ to NRZI Encoder
          4. Binary to MLT-3 Converter
        2. 100BASE-TX Receiver
      4. 8.4.4  100BASE-FX
        1. 100BASE-FX Transmit
        2. 100BASE-FX Receive
      5. 8.4.5  10BASE-Te
        1. Squelch
        2. Normal Link Pulse Detection and Generation
        3. Jabber
        4. Active Link Polarity Detection and Correction
      6. 8.4.6  Auto-Negotiation (Speed / Duplex Selection)
      7. 8.4.7  Auto-MDIX Resolution
      8. 8.4.8  Loopback Modes
        1. Near-End Loopback
        2. MII Loopback
        3. PCS Loopback
        4. Digital Loopback
        5. Analog Loopback
        6. Far-End (Reverse) Loopback
      9. 8.4.9  BIST Configurations
      10. 8.4.10 Cable Diagnostics
        1. TDR
      11. 8.4.11 Fast Link Down Functionality
    5. 8.5 Programming
      1. 8.5.1 Hardware Bootstrap Configurations
      2. 8.5.2 LED Configuration
      3. 8.5.3 PHY Address Configuration
    6. 8.6 Register Maps
  9. Application and Implementation
    1. 9.1 Application Information
    2. 9.2 Typical Applications
      1. 9.2.1 TPI Network Circuit
        1. Design Requirements
        2. Detailed Design Procedure
        3. Application Curves
      2. 9.2.2 Fiber Network Circuit
        1. Design Requirements
          1. Clock Requirements
            1. Oscillator
            2. Crystal
        2. Detailed Design Procedure
          1. MII Layout Guidelines
          2. RMII Layout Guidelines
          3. RGMII Layout Guidelines
          4. MDI Layout Guidelines
        3. Application Curves
  10. 10Power Supply Recommendations
    1. 10.1 Power Supply Characteristics
  11. 11Layout
    1. 11.1 Layout Guidelines
      1. 11.1.1 Signal Traces
      2. 11.1.2 Return Path
      3. 11.1.3 Transformer Layout
        1. Transformer Recommendations
      4. 11.1.4 Metal Pour
      5. 11.1.5 PCB Layer Stacking
    2. 11.2 Layout Example
  12. 12Device and Documentation Support
    1. 12.1 Related Links
    2. 12.2 Receiving Notification of Documentation Updates
    3. 12.3 Support Resources
    4. 12.4 Trademarks
    5. 12.5 Electrostatic Discharge Caution
    6. 12.6 Glossary
  13. 13Mechanical, Packaging, and Orderable Information
    1. 13.1 Package Option Addendum
      1. 13.1.1 Packaging Information
      2. 13.1.2 Tape and Reel Information

Package Options

Mechanical Data (Package|Pins)
Thermal pad, mechanical data (Package|Pins)
Orderable Information

Reduced Media Independent Interface (RMII)

The DP83822 incorporates the Reduced Media Independent Interface (RMII) as specified in the RMII specification from the RMII consortium. The purpose of this interface is to provide a reduced pin count alternative to the IEEE 802.3u MII as specified in Clause 22. Architecturally, the RMII specification provides an additional reconciliation layer on either side of the MII, but can be implemented in the absence of an MII. The DP83822 offers two types of RMII operations: RMII Slave and RMII Master. In RMII Slave operation, the DP83822 operates off of a 50-MHz CMOS-level oscillator connected to the XI pin and shares the same clock as the MAC. In RMII Master operation, the DP83822 operates off of either a 25-MHz CMOS-level oscillator connected to XI pin or a 25-MHz crystal connected across XI and XO pins. A 50-MHz output clock referenced from any of the three DP83822 GPIOs is connected to the MAC.


If RMII Master mode is configured through bootstraps, a 50-MHz output clock will automatically be enabled on RX_D3 (GPIO3).

The RMII specification has the following characteristics:

  • Supports 100BASE-FX, 100BASE-TX and 10BASE-Te.
  • Single clock reference sourced from the MAC to PHY (or from an external source)
  • Provides independent 2-bit wide transmit and receive data paths
  • Uses CMOS signal levels, the same levels as the MII interface

In this mode, data transfers are two bits for every clock cycle using the internal 50-MHz reference clock for both transmit and receive paths.

The RMII signals are summarized below:

Table 8-2 RMII Signals
Data SignalsTX_D[1:0]
Transmit and Receive SignalsTX_EN
GUID-79F70463-8CB9-4640-914C-C3A2B2628A5E-low.gifFigure 8-5 RMII Slave Signaling
GUID-E7F22B5E-DCFB-4376-8569-A73208DEDCA9-low.gifFigure 8-6 RMII Master Signaling

Data on TX_D[1:0] are latched at the PHY with reference to the clock edges on the XI pin. Data on RX_D[1:0] are latched at the MAC with reference to the same clock edges on the XI pin. RMII operates at the same speed in 10BASE-Te, 100BASE-TX and 100BASE-FX. In 10BASE-Te the data is 10 times slower than the reference clock, so transmit data is sampled every 10 clock cycles. Likewise, receive data is generated on every 10th clock so that an attached MAC device can sample the data every 10 clock cycles.

In addition, RMII mode supplies an RX_DV signal that allows a simpler method of recovering receive data without the need to separate RX_DV from the CRS_DV indication. RX_ER is also supported even though it is not required by the RMII specification.

RMII includes a programmable elastic buffer to adjust for the frequency differences between the reference clock and the recovered receive clock. The programmable elastic buffer minimizes internal propagation delay based on expected maximum packet size and clock accuracy.

Table below indicates how to program the buffer FIFO based on the expected maximum packet size and clock accuracy. It assumes that the RMII reference clock and the far-end transmitter clock have the same accuracy.

Table 8-3 Recommended RMII Packet Sizes
AT ±50 ppm
AT ±100 ppm
1 (4-bits)2 bits2400 bytes1200 bytes
2 (8-bits)6 bits7200 bytes3600 bytes
3 (12-bits)10 bits12000 bytes6000 bytes
4 (16-bits)14 bits16800 bytes8400 bytes