SI-Ethernet User Guide
149
Issue: 3
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7.3.5
General guidelines for synchronous cyclic data
The following guidelines provide a simple way of specifying a network supporting synchronous
cyclic data that offers accurate synchronization and guaranteed determinism, whilst maintaining
compatibility with standard Ethernet traffic.
•
Limit daisy chains to 10 drives
•
Where more than 10 drives are used, create a tree structure using a switch
•
Any Ethernet switches must support IEEE1588 V2
•
Segregate the network using VLANs and gateways
•
Assign one device to be the synchronization master for each segregated network
7.3.6
Segregating the network
If synchronous cyclic links are used, for best reliability it is sensible to segregate the network. This
means:
•
Assign one (or more) drive(s) to be a gateway, which ensures messages entering the
segregated section are stripped of any existing prioritisation information. (See
Gateway Mode
(
S.02.025
)
•
Ensure that
VLAN
(Virtual Local Area Network) is enabled on all devices so that synchronous
data can be prioritized as it is passed between switches. (See
VLAN Enable
(
S.02.030
) and
Drive VLAN ID
(
S.02.031
))
•
Use multiple Master Clock Domains. (See
Master Clock Domain
(
S.11.002
))
7.3.7
Synchronization master
If a synchronous cyclic link is used then one device must be a synchronous master, if this is an
existing 3
rd
party device then, to minimize the initialization time, all other devices/drives on the
network should not be allowed to become the synchronous master. To disable the drive from
becoming the synchronous master then set the value in
Preferred Sync Master
(
S.11.001
) to 0, this
ensures the drive does not become the synchronous master.
If there is no existing synchronous master then a suitable drive should be chosen (see
Preferred
Sync Master
(
S.11.001
)), in choosing which drive to be the synchronous master, the physical
position of the drives and network layout should be considered so as to minimize the number of
switches each message has to pass through.
A typical segregated network using VLANs and gateways consisting of three separate sections of a
machine controlled by one master PLC is shown in the following diagram.
Содержание Unidrive M600
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