ABB FEPL-02 Ethernet POWERLINK, Руководство пользователя

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92 Communication protocol
An Ethernet POWERLINK cycle consists of three phases. During
the start phase, the MN sends a Start of Cycle Frame (SoC) signal
to all CNs to synchronize the devices. Payload data exchange then
proceeds in the second phase, the isochronous phase. The third
phase, the asynchronous phase, allows the transfer of large
packets that are not time-critical, for example, parametrization
data.
Ethernet POWERLINK state machine
In Ethernet POWERLINK, a Controlled Node starts up by a
common initialization process. All the states are valid when the
device is powered, and they are substates of the
NMT_GS_POWERED superstate.

NMT_GS_INITIALISATION
After system start, the device automatically assumes this state and
network functionality begins. NMT_GS_INITIALISATION and all its
substates are only internal states of the device.
PReq
CN2
Asynchronous
phase Isochronous phase
PReq
CN1
PRes
CN1
PRes
CN2
SoC PReq
CNn
PRes
CNn
SoA
Async
data
MN
CN
Ethernet POWERLINK communication cycle
Start
phase