Rockwell Automation 1791DS-IBxxxx Guard I/O DeviceNet Safety Modules - Manual (Page 72)

72 Rockwell Automation Publication 1791DS-UM001J-EN-P - May 2013
Chapter 5 Configure Modules with the Logix Designer Application
3. In the Requested Packet Interval (RPI) box, enter the input connection
RPI to support your application (between 6 and 500 ms).
Selecting too small an RPI unnecessarily consumes network bandwidth;
selecting too large an RPI increases safety reaction time. Selecting the
appropriate RPI results in a system with optimized performance.
As an example, a safety input module with only ESTOP switches
connected to it generally may work well with settings of 50…100 ms.
An input module with a light curtain guarding a hazard may need the
fastest response that is possible.
A connection status tag exists for every connection.
When the connection reaction time limit and requested packet interval are set
appropriately, this status tag always remains LO. Monitor all connection status
bits to verify that they are not going HI intermittently due to timeouts.
IMPORTANT Analyze each safety channel to determine what is appropriate. The
default Time-out Multiplier of 2 and Network Delay Multiplier of 200
will create an input-connection reaction time limit of four times the
RPI and an output-connection reaction time limit of three times the
RPI. Changes to these parameters should be approved by a safety
administrator.
TIP We recommend keeping the Time-out Multiplier and Network
Delay Multiplier at their default values of 2 and 200.