214 Rockwell Automation Publication 1715-UM001J-EN-P - December 2020
Chapter 7 1715 Redundant I/O System in SIL 2 Safety Applications
The default value for the CRTL is 10,000 ms. The valid range is
1000…60,000 ms.
Considerations for Setting the CRTL
The value of the CRTL forms part of the safety considerations for the system.
You are responsible for calculating and verifying that the CRTL meets the
safety reaction time for your safety function.
• In a 1715 system, the CRTL value is assigned to individual modules during
module configuration.
• If the input CRTL is not met, the controller presents fail-safe input values
to the application logic. Each time a valid packet is received from an
input module, the controller resets the CRTL. If the CRTL ever times out,
the controllers present fail-safe input values to the application logic.
• Each time a valid packet is received from the controller, the output
module resets the CRTL. If the CRTL ever times out, the output module
assumes the fail-safe state.
• It is recommended that the CRTL remain at the default of four times the
RPI so that one invalid packet does not put the system into the safe state.
IMPORTANT
When online, the Reset button on the SIL 2 Safety tab appears
solid when only the output data on any 1715 output module must
be reset. See pages 216
and 276.
The Reset button resets only output data for output modules, that
is, the 1715-OF8I and 1715-OB8DE module outputs.
To reset inputs for all 1715 modules, you must use the Reset Input
parameter within the Add-On Instructions. See Performing a SIL 2
Reset on page 276.
IMPORTANT
For information about how to configure the safety reaction time
for your safety application, see page 217
.
IMPORTANT
The default fail-safe state for all 1715 modules is de-energized.
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