Rockwell Automation 1440-RMA00-04RC XM-440 Master Relay Module - Manual (Page 43)

Rockwell Automation Publication GMSI10-UM009D-EN-P - June 2011
Configuration Parameters 43
Interscan Delay Defines the amount of time the XM-440 pauses
between consecutive scans. This means that the
XM-440 will poll all the slaves in its scanlist, then
pause for interscan delay, then begin the next series
of polls.
During the pause time, slave responses and other
network traffic can access the network. This other
network traffic could be another primary master
scanning the network or lower priority messages (for
example, network browsing, configuration
upload/download).
Note that the interscan delay also affects the rate at
which the XM-440 requests Poll data from the XM
slave measurement modules. The Poll request rate is
equal to the scan time plus the interscan delay. The
scan time is dependant on the number of modules in
the scanlist, the amount of competing network
traffic, and the ISD.
Enter a value from 2 to 9,000
milliseconds. The default is 400
milliseconds.
Note:
• Decrease the interscan delay value
if you need to increase the data
refresh rate for devices (e.g.
PanelView module) on the network
that are listening for the Poll data
that is being collected by the
XM-440. If you do not have a device
listening for the Poll data, then there
is no need to decrease the interscan
delay.
• Increase the interscan delay value if
you want more time for slave
responses and other network traffic.
For example, if your network
browsing and configuration tools
seem sluggish or unresponsive, it
may be because the higher priority
scan traffic is blocking the lower
priority traffic. Increasing the
interscan delay will allow the lower
priority traffic more time to access
the network.
Or, if you have many slaves in the
scanlist, the XM-440 may have
trouble keeping connections open to
the slave devices. Increasing the
interscan delay can relieve this
problem because the slaves will
have more time to access the
network.
XM Network Node List Parameters
Parameter Name Description Values/Comments