Rockwell Automation Publication 1769-UM022C-EN-P - June 2018
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Add, Configure, Monitor, and Replace CIP Safety I/O Devices
Chapter 7
Timeout Multiplier
The Timeout Multiplier determines the number of RPIs to wait for a packet
before declaring a connection timeout. This translates into the number of
messages that can be lost before a connection error is declared.
For example, a timeout multiplier of 1 indicates that messages must be received
during each RPI interval. A Timeout Multiplier of 2 indicates that 1 message
can be lost as long as at least 1 message is received in 2 times the RPI (2 x RPI).
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
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%
