BECKHOFF EtherCAT Technology Section I - Manual (Page 106)

Error Counters
I-86 Slave Controller – Technology
14.1 Frame error detection
EtherCAT frame error detection takes place at three functional blocks, at the physical layer (device),
inside the Auto-Forwarder and inside the EtherCAT Processing Unit. The following errors are detected
by these units:
Table 51: Errors Detected by Physical Layer, Auto-Forwarder, and EtherCAT Processing Unit
Physical Layer Auto-Forwarder EtherCAT Processing Unit
Registers 0x301/3/5/7 Registers 0x300/2/4/8 (original
error) or registers 0x308/9/A/B
(forwarded error)
Registers 0x30C
RX Errors:

MII/RMII:
RX_ER event

EBUS:
EBUS/Manchester code
violations (refer to
chapter 6.6)

Physical Layer Errors (RX
Errors)

Too long frames
(> ~ 2000 Byte)

FIFO overrun/underrun

CRC errors

Frames without Ethernet SOF

Physical Layer Errors of
input port

Auto-Forwarder Errors of
input port

EtherCAT frame length errors
(e.g., frame ends although
more header/data bytes are
expected)

Too short frames (< 64 Byte)

Non-EtherCAT frames if
register 0x0100[0]=1

Circulating bit=1 and port 0
automatically closed
Any of the above errors will have these consequences:

The frame transmission is aborted (a frame with an RX Error at the beginning is truncated). The
CRC of the transmitted data is modified (or appended) so that it becomes bad. A special marking
for Forwarded Errors is added.

The EtherCAT Processing Unit discards register operations, e.g., write operations to registers,
SyncManager buffer changes, etc.. RAM areas will be written, because they do not have a
shadow buffer for write data like registers.

Error counters are increased.
Refer to Application Note “Frequently Asked Questions and Troubleshooting” for more advice
regarding error counter interpretation. The Application Note is available at the Beckhoff website
(
http://www.beckhoff.com ).
14.2 Errors and Forwarded Errors
The ESCs distinguish errors initially detected by an ESC and forwarded errors detected by a previous
ESC. This is useful for error location when interpreting the RX Error/Forwarded RX Error counters.
The first device detecting an error (e.g., a CRC error or an RX Error of the physical layer), will discard
register operations and count a port error (0x0300-0x0307). The outgoing frame gets a special
marking, consisting of one extra nibble added after the (invalid) CRC.
A device receiving a frame with a CRC error and an additional nibble will also discard register
operations, but it will count one Forwarded RX Error instead of a normal port error.
NOTE: A forwarded error is sometimes called “green error”, the initial error is sometimes called “red error”. A
physical layer RX Error is always a “red error”, because it could not have been forwarded.