Rockwell Automation 2711E PanelBuilder 1400e Modbus Communications - Manual (Page 29)

4–6 Defining Communications
Publication 2711E-6.12 – November 1997
Foreground and Background Period
The period specifies, in seconds, how often the device address
will be scanned. A foreground period applies to tags used on the
current screen, to the alarm and information window tags, and to
the tags under the PLC Controlled tab in the PLC I/O Control
dialog. The background scan period applies to tags used in all
other screens in the system. The valid range of values is 0 to
86,400 seconds (24 hours), with a 0.1 second resolution.
To specify a period, type a number. You can use fractions of a
second. For example, 0.6 means scan every six-tenths of a
second. Keep the background rate slow so as not to slow down
network traffic.
Tip: For more information about optimizing Modbus network
traffic, refer to your network user documentation. Also see
“Guidelines for Configuring Scan Classes” in Chapter 2,
“Planning Applications,” in the PanelBuilder 1400e
Configuration Software for Windows User Manual.
Note: If a tag is being used by both a foreground and background
component, the tag will be scanned at the foreground rate.
2. To save the information you’ve configured, choose OK.
Note: If you change the name of a scan class used by tags, you
have the option of automatically updating the tags with the new
name.
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