Allen-Bradley GuardLogix 5570 User Manual page 83

Network Delay Multiplier
The Network Delay Multiplier defines the message transport time that is
enforced by the CIP Safety protocol. The Network Delay Multiplier specifies
the round-trip delay from the producer to the consumer and the acknowledge
back to the producer. You can use the Network Delay Multiplier to reduce or
increase the Connection Reaction Time Limit in cases where the enforced
message transport time is significantly less or more than the RPI. For example,
adjusting the Network Delay Multiplier can be helpful when the RPI of an
output connection is the same as a lengthy safety task period.
For cases where the input RPI or output RPI are relatively slow or fast as
compared to the enforced message delay time, the Network Delay Multiplier
can be approximated by using one of the two methods.
Method 1: Use the ratio between the input RPI and the safety task period. Use
this method only when all of the following conditions apply:
• If the path or delay is approximately equal to the output path or delay.
• The input RPI has been configured so that the actual input message
transport time is less than the input RPI.
• The safety task period is slow relative to the Input RPI.
Under these conditions, the Output Network Delay Multiplier can be
approximated as follows:
Input Network Delay Multiplier x [Input RPI  Safety Task Period]
EXAMPLE Calculate the Approximate Output Network Delay
Rockwell Automation Publication 1756-UM022D-EN-P - May 2017
Add, Configure, Monitor, and Replace CIP Safety I/O Devices
Multiplier
If:
Input RPI = 10 ms
Input Network Delay Multiplier = 200%
Safety Task Period = 20 ms
Then, the Output Network Delay Multiplier equals:
200% x [10  20] = 100%
Chapter 5
83