Rockwell Automation Publication 5094-UM001E-EN-P - April 2020 31
Digital I/O Module Operation in a Logix 5000 Control System Chapter 1
Requested Packet Interval
The requested packet interval (RPI) is a configurable parameter that defines a
rate at which the owner-controller and the module exchange data. You set the
RPI value during initial module configuration and can adjust it as necessary after
module operation has begun.
The valid RPI values for FLEX 5000 I/O safety modules are 2…500 ms.
Connection Reaction Time Limit With FLEX 5000 I/O Safety Modules
Setting the RPI on FLEX 5000 I/O safety modules is not as straightforward as
setting it on FLEX 5000 I/O digital modules. With FLEX 5000 I/O safety
modules, the Connection Reaction Time Limit configuration affects the RPI
that is used for a module.
The Connection Reaction Time Limit defines the predicted period of safety
packets on the associated connection. If the Max Network Delay exceeds the
Connection Reaction Time Limit, a connection fault occurs.
By default, the Connection Reaction Time Limit is four times the RPI.
Use the default values for Timeout Multiplier (2) and Network Delay Multiplier
(200). The Network Delay Multiplier value is in terms of percentage. Thus, 200
means 200%.
For more information on specifying RPI rates, see the following:
• FLEX 5000 I/O safety I/O modules - page 31
• Logix 5000 Controllers Design Considerations Reference Manual,
publication 1756-RM094
IMPORTANT You can change the RPI while the project is online. If you change the RPI
while the project is online, however, the connection to the module is closed
and reopened in one of the following ways:
• You inhibit the connection to the module, change the RPI value, and
uninhibit the connection.
• You change the RPI value. In this case, the connection is closed and
reopened immediately after you apply the change to the module
configuration.
IMPORTANT To determine what is appropriate, analyze each safety channel. The default
Timeout Multiplier of 2 and Network Delay Multiplier of 200 creates a worst-
case input connection reaction time limit of 4 times the RPI, and an output
connection reaction time limit of 3 times the RPI.
Changes to these parameters must be approved only after a thorough review
by a safety administrator.
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