166 Rockwell Automation Publication 1769-UM021G-EN-P - October 2015
Chapter 7 Use I/O Modules with CompactLogix 5370 L1 Controllers
• If modules of different types are removed and returned to the wrong
locations, attempts to connect to these modules fail during verification of
Electronic Keying.
• If modules of the same type are removed and returned to the wrong
locations, they accept connections from the controller and reconfigure
with the correct data once they pass their electronic keying check.
Estimate Requested Packet Interval
The requested packet interval (RPI) defines the frequency at which the
controller sends data to and receives data from I/O modules. You set an RPI rate
for each I/O module in your system.
The CompactLogix 5370 L1 controllers attempt to scan an I/O module at the
configured RPI rate. For individual I/O modules, a Module RPI Overlap
minor
fault occurs if there are enough I/O modules with RPI rates set too fast that they
cannot all be serviced in the allotted interval.
The configuration parameters for a system determine the impact on actual RPI
rates. These configuration factors can affect the effective scan frequency for any
individual module:
• Other 1734 POINT I/O module RPI rate settings
• Number of other 1734 POINT I/O modules in the system
• Types of other 1734 POINT I/O modules in the system
• Application user task priorities
If Electronic Keying is set to Disable Keying, no verification of electronic
keying occurs and unintended control can occur.
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