BECKHOFF EtherCAT Technology Section I - Manual (Page 33)

Frame Processing
Slave Controller – Technology I-13
Auto close (manual open)
The port is closed depending on the link state, i.e., if the link is lost, the loop will be closed (auto
close). If the link is established, the loop will not be automatically opened, instead, it will remain closed
(closed wait state). Typically, the port has to be opened by the master explicitly by writing the loop
configuration again to the ESC DL Control register 0x0100. This write access has to enter the ESC via
a different open port. There is an additional fallback option for opening the port: if a valid Ethernet
frame is received at the closed port in Auto close mode, it will also be opened after the CRC is
received correctly, without explicit master interaction.
open
closed
closed
wait
link lost
a) master writes loop
configuration again to AL Control
register (via another open port)
or
b) a valid Ethernet frame is
received at this port
link lost
link establishd
Figure 4: Auto close loop state transitions
A port is considered open if the port is available, i.e., it is enabled in the configuration, and one of the
following conditions is met:

The loop setting in the DL Control register is Auto and there is an active link at the port.

The loop setting in the DL Control register is Auto close and there is an active link at the port and
the DL Control register was written again after the link was established.

The loop setting in the DL Control register is Auto close and there is an active link at the port and
a valid frame was received at this port after the link was established.

The loop setting in the DL control register is Always open
A port is considered closed if one of the following conditions is met:

The port is not available or not enabled in the configuration.

The loop setting in the DL Control register is Auto and there is no active link at the port.

The loop setting in the DL Control register is Auto close and there is no active link at the port or
the DL Control register was not written again after the link was established

The loop setting in the DL Control register is Always closed
NOTE: If all ports are closed (either manually or automatically), port 0 will be opened as the recovery port.
Reading and writing via this port is possible, although the DL status register reflects the correct status. This can
be used to correct DL control register settings.
Registers used for loop control and loop/link status are listed in Table 8.
Table 8: Registers for Loop Control and Loop/Link Status
Register Address Name Description
0x0100[15:8] ESC DL Control Loop control/loop setting
0x0110[15:4] ESC DL Status Loop and link status
0x0518:0x051B PHY Port status PHY Management link status