BECKHOFF EtherCAT Technology Section I - Manual (Page 26)

EtherCAT Protocol
I-6 Slave Controller – Technology
Table 3: EtherCAT Datagram
Field Data Type Value/Description
Cmd BYTE EtherCAT Command Type (see 2.5)
Idx BYTE The index is a numeric identifier used by the master for
identification of duplicates/lost datagrams. It shall not be changed
by EtherCAT slaves
Address BYTE[4] Address (Auto Increment, Configured Station Address, or Logical
Address, see 2.3)
Len 11 bit Length of the following data within this datagram
R 3 bit Reserved, 0
C 1 bit Circulating frame (see 3.5):
0:
Frame is not circulating
1: Frame has circulated once
M 1 bit More EtherCAT datagrams
0:
Last EtherCAT datagram
1: More EtherCAT datagrams will follow
IRQ WORD EtherCAT Event Request registers of all slaves combined with a
logical OR
Data BYTE[n] Read/Write Data
WKC WORD Working Counter (see 2.4)
2.3 EtherCAT Addressing Modes
Two addressing modes of EtherCAT devices are supported within one segment: device addressing
and logical addressing. Three device addressing modes are available: auto increment addressing,
configured station address, and broadcast. EtherCAT devices can have up to two configured station
addresses, one is assigned by the master (Configured Station Address), the other one is stored in the
SII EEPROM and can be changed by the slave application (Configured Station Alias address). The
EEPROM setting for the Configured Station Alias address is only taken over at the first EEPROM
loading after power-on or reset.
Table 4: EtherCAT Addressing Modes
Mode Field Data Type Value/Description
Auto Increment
Address
Position WORD Each slave increments Position.
Slave is addressed if Position = 0.
Offset WORD Local register or memory address of the ESC
Configured
Station Address
Address WORD Slave is addressed if Address matches
Configured Station Address or Configured
Station Alias (if enabled).
Offset WORD Local register or memory address of the ESC
Broadcast Position WORD Each slave increments Position (not used for
addressing)
Offset WORD Local register or memory address of the ESC
Logical Address Address DWORD Logical Address (configured by FMMUs)
Slave is addressed if FMMU configuration
matches Address.