Rockwell Automation 2708-DH5B2L_DH5B4L Attended Workstation - Manual (Page 28)

Chapter 2
Installing a Network
2–15
Figure 2.12
Large Network Configuration with Alternate Masters
Host 1 M—A—C—C—C—W—C—C—W—C—C—C
W Workstation
S Submaster
M Master
C Concentrator
A Alternate Master
AS Alternate Submaster
Indicates RS-232 or RS-422 connection
Indicates RS-485 backbone
Indicates a tributary
W
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W
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S
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S
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AS
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W
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S
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W
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W
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W
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S
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AS
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W
Key:
W
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W
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AS
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S
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Host 2
An Alternate Submaster will allow the communication operations to continue
through a secondary Concentrator if the primary Concentrator becomes
inoperable or is removed from the network.
Networks Over Telecommunications Lines
It is possible to configure a workstation network which spans multiple
buildings, outposts, or sub-stations located at remote sites. Switched or
leased telephone lines can be used with asynchronous modems to provide
communication links for such a network.
Asynchronous short-haul modems may be used to extend the normal RS-232
communication distance from 100 feet to as much as several miles. To use
modems for communications between a Concentrator and Submaster the
workstations MUST have an RS-232 communication port (Workstation
Catalog No. 2708-DH5B2L). A modem cable must be correctly connected to
TXD, RXD, RTS, CTS, DSR, DTR, and GROUND signals (see Appendix
D). The COMM BAUD RATE parameter must be changed to the same baud
rate as the modem.