Rockwell Automation 2708-DH5B2L_DH5B4L Attended Workstation - Manual (Page 73)

Chapter 7
Network Design
7–3
When installing large networks, you should consider redundant
communication links in order to protect against workstation failures. This
involves establishing certain workstations as “Alternate Masters” and certain
workstations as “Alternate Submasters”. Configuring a large network with
Alternate Masters will allow the Alternate workstation to take over
communication operations if the designated Master becomes inoperable or is
removed from the network. An Alternate Host provides full redundancy for
collection in the event of a host failure.
A large network configuration with Alternate Masters could look like the
following:
Figure 7.3
Large Network Configuration with Alternate Masters
Host M—A—C—C—W—C—W—C—W—W—C—C
W
|
W
|
S
|
|
S
|
W
|
W
|
S
|
W
|
W
|
W
|
S
|
A
|
W
W
|
W
|
W
|
S
|
Host
Indicates RS-232 connect
Indicates RS-485 backbone
Indicates a tributary W Workstation
S Submaster
C Concentrator
M Master
A Alternate
Key:
Note: All references to RS-232 should be understood to mean RS-422 if the
workstation’s COM1 port was ordered as RS-422.
Fault-Tolerant Networks