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5.2
5.2.1
Ethernet Powerlink communication
In an Ethernet POWERLINK network, one of the nodes, for example a PLC, is designat-
ed to function as the MN, the master in the network. All other devices operate as CNs,
slaves in the network. The MN defines the clock pulse for the synchronization of all de-
vices and manages the data communication cycle. In the course of one clock cycle within
which all nodes are addressed, the MN sends Poll Requests (PReq) to all CNs, one after
another. They reply immediately to the prompts with Poll Responses (PRes).
The following time phases exist within one cycle:
- Isochronous phase
- Asynchronous phase
- Idle phase
The MN first sends a Start of Cycle Frame (SoC) signal to all CNs to synchronize the de-
vices. Payload data exchange then proceeds in the isochronous phase. The asynchronous
phase, allows the transfer of large packets that are not time-critical, for example param-
eterisation data or transfer of IP-based protocols like TCP or UDP. The Idle phase can
be 0. It's possibly for the MN to multiplex the time slots in the isochronous phase, in or-
der to service some CN's more often than others. During system start-up the MN applies
a reduced POWERLINK cycle, without the isochronous phase, in order to configure the
CNs with SDO communication.
For further information, please refer to the Ethernet POWERLINK communication pro-
file specification "EPSG_DS_301_V-1-1-0_01.pdf", available at the EPSG website
www.ethernet-powerlink.org.
Managing Node
SoC
Controlled Node
SoC
PReq
to CN n
PRes
from CN 1
JVL Industri Elektronik A/S - User Manual - Ethernet for MAC and MIS motors
Protocol specifications
Isochronous Phase
PReq
PReq
PReq
to CN 1
to CN 1
to CN 2
PRes
from CN 1
Powerlink cycle
Start of Cyclic :
Sent from MN, multi-cast to all Controlled Nodes
Poll Request :
Sent from MN, uni-cast to each Controlled Node
Poll Responce :
Sent from CN, multi-cast to all nodes
PReq
to CN n
PRes
PRes
from CN 2
from CN n
PRes
Poll Responce :
from MN
Sent from MN, multi-cast to all nodes
Start of Acyclic :
SoA
Sent from MN, multi-cast to all Controlled Nodes
Async.
Async data :
send
Sent by any CN, invited by Managing Node
Asynchronous
Phase
PRes
SoA
from MN
Async.
send
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