DP83869HM: Using DP83869HM for "EtherCAT (100Mbit/s)"

Daisuke-san

For EtherCAT (100Mbit/s), the PHY has to provide an MII (or RMII/RGMII1) interface. MII is the preferred method due to its lower latency. But configuring the DP83869HM into MII is a little tricky, please reference Section 1.9 MII-to-Copper in Understanding Different Modes of Operation in DP83869. The main point of that section is that Register access is required to set up MII in the DP83869HM. Register 0x01DF must be set to 0x0060. Please read the section for more details. But Beckhoff requires that the PHY configuration must not rely on configuration via the MII management interface, i.e., required features must be enabled after power-on3, e.g., by default or by strapping options.

So for EtherCat (100Mbit/s), please use DP83826A, which was just released. It can support EtherCat(100Mbit/s) through the strapping options.

Thanks

David

Daisuke-san

Shane's response in the e2e thread you found summarizes the difference between the DP83826 and DP83826A and I quote below

DP83826AI has improved EMC performance over DP83826I.

• DP83826A has ESD performance rated for Class A requirements at 8kV.
  • DP83826I supports 8kV ESD testing but does not meet Class A standards 
• DP83826A adds an additional strap on RX_CLK to better configure the device for preventing link drop.
  • This gives more options for the FLD mechanisms that will cause the PHY to drop a link. 

So if you need to meet the IEC +/-8kV Class A requirement, then I would use DP83826A.Otherwise you can stay with DP83826.

DP83826A is also included in the Beckhoff PHY selection guide.

The DP83826/A has the lowest and most deterministic latency of all Ethernet PHYs and it also provides longer cable reach of 150m. Is there a specific feature the customer is looking for in DP83826/A?

For rollover from KSZ8081 to DP83826, please see this app note.

Thanks

David