Rockwell Automation 1756-IH16ISOE ControlLogix Sequence of Events Module - Manual (Page 26)

Publication 1756-UM528A-EN-P - April 2004
2-10 How Does the Sequence of Events Module Operate in a ControlLogix System?
When selecting values for the remotely located module’s RPI,
system throughput is optimized when its RPI value is a power of 2
times the current NUT running on ControlNet.
For example, Table 2.5 shows recommended RPI values for a system
using a NUT of 5mS:
Remote Input Modules Connected Via EtherNet/IP
When the Sequence of Events module is connected to the
owner-controller via an EtherNet/IP network, data is transferred to
the owner-controller in the following way:
• At the RPI or on an Enable CST Capture event, the module
multicasts data within its own chassis.
• The 1756-ENBT module in the remote chassis immediately
sends the module’s data over the network to the
owner-controller as long as it has not sent data within a time
frame that is 1/4 the value of the digital input module’s RPI.
For example, if a Sequence of Events module uses an RPI =
100ms, the 1756-ENBT module only sends module data
immediately on receiving it if another data packet was not
sent within the last 25ms.
Chapter Summary and
What’s Next In this chapter you read about how the Sequence of Events module
operates in a ControlLogix system.
Chapter 3 explains the Installing the Sequence of Events Module.
Table 2.5 Recommended RPI Values for System Using NUT of 5mS
NUT=5mS x2 0
x2
1
x2
2
x2
3
x2
4
x2
5
x2
6
x2
7
Optimal
RPI Values
(mS) 5mS 10mS 20mS 40mS 80mS 160mS 320mS 640mS