Programming manual SCU-series
HB-37500-820-10-12F-EN SCU Programming manual
Page 19 of 252
Status: 19.03.2021
3.2.1.1. EtherCAT data transfer
Basically, a difference is made between process data that must be transferred cyclically, and
acyclic data, such as configuration data and diagnostic data.
The cyclic process data are assigned to the PDOs (Process Data Objects).
Length and content of the PDOs can be either fixed or variable. The variable content is fixed by the
PDO mapping. The PDO’s possibilities are fixed by the individual participant’s descri
ption file (ESI
file).
Primarily, acyclic data services are SDOs (Service Data Objects), but they can also be EoE
(Ethernet over EtherCAT) or FoE (File over EtherCAT).Also here, the possibilities of the acyclic
services are fixed by the individual partici
pant’s description file (ESI file).
3.2.2. FSoE
FSoE (Fail Safe over EtherCAT) is the safe data transfer via the EtherCAT network. User data are
compiled into data packages, and are supplemented with an additionally transferred checksum.
The transfer is carried out every 1ms.
Furthermore, the transfer is monitored via timer (Watchdog) which is checked in every network
participant. Thus, any interruption of the data transfer can be safely recognized.
The checksum is calculated with a CRC 16 (16-Bit-Cyclic Redundancy Check), and allows to
recognize a fault with a residual error probability of < 10
-9
and thus allows a safe data transfer
suitable for the use up to PL e or SIL 3.
Among others, the following units are suitable as FSoE-Slaves:
•
SSB = Safe Sensor Box Slave unit by BBH to read 6 axis
•
SDU = Safe Drive Unit
Slave unit by BBH to read one axis
•
SIO = Safe IO
Slave unit by BBH to read IOs
•
EL 1904
Slave unit by Beckhoff (to read entries)
•
EL 2904
Slave unit by Beckhoff (to switch outputs)
•
AX 5805
Slave unit by Beckhoff (to read axis data)
•
AX 5806
Slave unit by Beckhoff (to read axis data)
•
SDC
Slave unit by LT-i (to read axis data and IOs)
In general, also units manufactured by other companies can be incorporated as FSoE Slaves if
they offer an FSoE communication.