SNLA344B June   2020  – March 2022 DP83826E , DP83826I

 

  1.   Trademarks
  2. 1Introduction
  3. 2 EtherCAT Specification Requirements
  4. 3Different Methods of Setting up the PHY
    1. 3.1 Using Serial Management Interface to Setup DP83826 PHY
    2.     6
    3. 3.2 Using Strap Configuration to Set Up DP83826 PHY for EtherCAT Configuration
  5. 4References
  6. 5Revision History

Introduction

When starting an EtherCAT® design, first review the Section I – Technology EtherCAT® Protocol, Physical Layer, EtherCAT® Processing Unit, FMMU, SyncManager, SII EEPROM, Distributed Clocks Data Sheet. This document describes how to connect an Ethernet PHY onto an EtherCAT® ESC. This document describes the needed interfaces between the ESC and the Ethernet PHYs, those interfaces are the PHY Management (PHY MI) and EtherCAT Interface and are illustrated in Figure 1 from the previously referenced data sheet. In chapter 4 (Physical Layer Common Features) and chapter 5 (Ethernet Physical Layer) The interface between the ESC and the PHY is described. Some key points to investigate here include:

  • ESC in reset state has to leave the PHY disabled (No link connection until active ESC)
  • MII interface has special use the pins TX_CLK,COL,CRS,TX_ER; for details, see table 14 (Special/Unused MII Interface signals).
    • EtherCAT® has a special setup to determine Link Detection in several steps; see section 5.6
  • LINK_MII signal, this is typically an LED output signal which indicate a 100 Mbit/s Full Duplex link
  • Enhanced link detection which is ensuring that the link signal is checked every approximately 10 µs; see section 5.6.2 for details

Another part to look into is the document EtherCAT PHY specification. This is found in the Application Note – PHY Selection Guide on the EtherCAT® home page. In this document the specifications and the recommendations of Ethernet PHY performance is documented the following lists and are a copy paste of that document version 2.6 (2017-10-04).

This document compares the EtherCAT® specification and recommendations in respect to the new TI PHY the DP83826. The first bullet is the EtherCAT® PHY specification requirement and the second bullet is the DP83826 compliance to the requirement.