Connection Reaction Time Limit
The Connection Reaction Time Limit (CRTL) is the maximum age of safety packets on the associated connection. If the age of the data that is used by the consuming device exceeds the CRTL, a connection fault occurs.
The CRTL is defined by the values in the following table.
Value | Default | Description |
|---|---|---|
Requested packet interval (RPI) | 10 ms (input RPI) | The RPI determines how often the input and output packets are placed on the network. |
Timeout multiplier | 2 | The timeout multiplier determines the number of retries before a timeout occurs. IMPORTANT: For any safety connection, do not set the timeout multiplier lower than 2. If the timeout multiplier is lower than 2, you risk the controller not meeting time coordination requirements during a loss of redundancy. |
Network delay multiplier | 200% | The network delay multiplier accounts for known delays on the network. When known delays occur, timeouts can be avoided with this parameter. |
If you adjust these values, then you can adjust the CRTL. If a valid packet is not received within the CRTL, the safety connection times out, and the input and output data is placed in the safe state (Off).
IMPORTANT:
The default values generate an input connection reaction time limit of 40 ms. If no edits are made to the defaults, verify this connection reaction time limit is used in the safety reaction time calculations.
IMPORTANT:
For applications with safety I/O, the default connection reaction time limit can result in connection loss to the safety I/O modules. In some cases, it is necessary to increase the values from their defaults. Make sure that you use the new connection reaction time limit in the safety reaction time calculations.
The following equations determine the CRTL:
Input Connection Reaction Time Limit = Input RPI x [Timeout Multiplier + Network Delay Multiplier]
Output Connection Reaction Time Limit = Safety Task Period x [Timeout Multiplier + Network Delay Multiplier - 1]
The CRTL is shown on the Safety view of the Module Properties dialog box.
Connection Reaction Time Limit
Specify the Requested Packet Interval (RPI)
The RPI specifies the period that data updates over a connection. For example, an input module produces data at the RPI that you assign.
For safety input connections, you can set the RPI on the Safety view of the Module Properties dialog box. The RPI is entered in 1 ms increments.
The CRTL is adjusted immediately when you change the RPI value.
Requested Packet Interval
For safety output connections, the RPI is fixed at the safety task period. If the corresponding CTRL is not satisfactory, you can adjust the safety task period on the Safety Task Properties dialog box.
For typical applications, the default CRTL for input connections of 4 x RPI and the default CRTL for output connections of 3 x RPI is usually sufficient. For more complex requirements, use the Advanced button to modify the CTRL parameters.
View the Maximum Observed Network Delay
The maximum observed network delay is shown on the Safety view of the Module Properties dialog box. When online, click Reset to reset the maximum observed network delay.
Reset the Max Observed Network Delay
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