Is the "full duplex" mode supported by the Ethernet ports of a PCD?

FAQ #101365

Since summer 2010 the PCD3 family (PCD3.M2xxx, PCD3.M3xxx, PCD3.M5xxx and PCD3.M6xxx) do support the "full-duplex mode" and Auto-MDIX on the Ethernet port.

The PCD systems PCD1.M2, PCD2.M5 and the PCD3.T665/665 as well as the MB Panels PCD7.D4xx do support the "full-duplex mode" and Auto-MDIX since the first hardware version.


The easiest way to detect wheter a PCD3 features the full duplex mode as well as Auto-MDIX is checking whether the RJ45 plug is equipped with LEDs. If it is, the PCD supports the full duplex mode as well as the Auto-MDIX feature (auto-crossing the signals).
In detail the following hardware version or later are required in order to support full duplex and Auto-MDIX:

  • The PCD3.M3xxx, PCD3.M5xxx and PCD3.M6xxx since hardware F.
  • The PCD3.M2x30A4T1 and PCD3.M2x30A4T3 since hardware B.
  • The PCD3.M2x30A4T5 since hardware C.

Before these hardware versions the PHY which was mounted on the PCD3.M3xxx, PCD3.M5xxx and PCD3.M6xxx CPUs was configured by hardware to work in half-duplex mode and not to support Auto-MDIX. As result, the half duplex mode was used even if the partner device was configured in auto negation mode and the port should be initialized in full duplex mode.
This was the case on all PCD3.M3xxx and PCD3.M5xxx up to hardware version E 4.


  • With "half-duplex": The data throughput is not devided by two because of this configuration as the limiting factor is not the the full/half duplex mode of the ethernet interface but rather the time it takes for the PCD to treat the received telegrams. The data throughput of the whole network is not affected either, since the next switch/hub will have an own port configuration for every port used (so on one port half-duplex can be used, and on another port full duplex can be used at the same time).
  • If the Auto-MDIX is supported it is not necessary to use a crossover cable for directly connecting e.g. a PC to a PCD, or a MB Panel to a PCD.


PCD3 / Txxx

PCD3 / _Firmware Classic

Communication / Ether-S-Bus

PCD7 / D4xx (MB Panel)

PCD1 / M2xx0

PCD2 / M5xxx

PCD7 / D4xxE (Energy Manager)

Last update: 31.05.2015 21:17

First release: 28.01.2010 15:55

Views: 28403

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