SNLA443 December   2023 DP83869HM

 

  1.   1
  2.   Abstract
  3.   Trademarks
  4. 1DP83869 Application Overview
  5. 2Troubleshooting the Application
    1. 2.1 Configuring Correct Operational Mode
    2. 2.2 Schematic and Layout Checklist
    3. 2.3 Component Checklist
    4. 2.4 Peripheral Pin Checks
      1. 2.4.1 Power Supplies
      2. 2.4.2 RBIAS Voltage and Resistance
      3. 2.4.3 Probe the XI Clock
      4. 2.4.4 Probe the RESET_N Signal
      5. 2.4.5 Probe the Strap Pins During Initialization
      6. 2.4.6 Probe the Serial Management Interface Signals (MDC, MDIO)
      7. 2.4.7 Probe the MDI Signals
    5. 2.5 Built-In Self Test with Various Loopback Modes
    6. 2.6 Debugging MAC Interface
      1. 2.6.1 RGMII
      2. 2.6.2 SGMII
  6. 3Operational Mode Clarification
    1. 3.1 Bridge Modes
    2. 3.2 Fiber Configuration
      1. 3.2.1 Fiber Registers
  7. 4Tools and References
    1. 4.1 DP83869HM Register Access
    2. 4.2 Extended Register Access
      1. 4.2.1 Read (No Post Increment) Operation
      2. 4.2.2 Write (No Post Increment) Operation
    3. 4.3 Software and Driver Debug on Linux
      1. 4.3.1 Common Terminal Outputs
  8. 5Summary
  9. 6References

2.6.2 SGMII

The Serial Gigabit Media Independent Interface (SGMII) provides a means of conveying network data and port speed between a 100/1000 PHY and a MAC with significantly less signal pins (4 or 6 pins) than required for GMII (24 pins) or RGMII (12 pins). The SGMII interface uses 1.25-Gbps LVDS differential signaling which has the added benefit of reducing EMI emissions relative to GMII or RGMII.

The SGMII interface includes Auto-Negotiation capability. Auto-Negotiation provides a mechanism for control information to be exchanged between the PHY and the MAC. This allows the interface to be automatically configured based on the media speed mode resolution on the MDI side. SGMII Auto-Negotiation is the default mode of the operation but can be disabled by writing register 0x14[7] = 0.

The SGMII Output spec included in the data sheet states an Output Differential Voltage which refers to the Peak-to-Peak, SO_P - SO_N. This means that the SO_P and SO_N signals are roughly ±0.55 V each.

Table 2-7 SGMII Output Spec
SGMII Output Min Typ Max Unit
Output Differential Voltage SO_P and SO_N, AC Coupled 0.95 1.00 1.05 V

All SGMII connections must be AC-coupled through a 0.1-μF capacitor.

GUID-41298790-FC65-40ED-8ED0-156F91A571BB-low.gif Figure 2-14 SGMII 4-Wire Connections