ABB FECA-01 EtherCAT, User Manual

Page: 89 / 148

Communication protocol 89
•
Logical read write (LRW)
•
Auto increment physical read multiple write (ARMW)
•
Configured address read multiple write (FRMW).
Addressing modes and FMMUs
There are a number of different addressing modes which can be
used by the master to communicate with EtherCAT slaves. As a full
slave, the adapter module supports the following addressing
modes:
•
Position addressing
The slave device is addressed via its physical position in the
EtherCAT
segment.
•
Node addressing
The slave device is addressed via a configured node address
assigned by the master during the start-up phase.
•
Logical addressing
The slaves are not addressed individually, but instead a
section of the segment-wide 4 GB logical address space is
addressed. This section may be used by any number of
slaves.
Fieldbus Memory Management Units (FMMUs) handle the local
assignment of physical slave memory addresses to logical
segment wide addresses. The slave FMMUs are configured by the
master. Each FMMU configuration contains a logical start address,
a physical memory start address, a bit length and a type that
specifies the direction of the mapping (input or output).
The adapter module has two FMMUs. The EtherCAT master can
use them for any purpose.