Allen-Bradley GuardPLC 1753, Safety Reference Manual

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Publication 1753-RM002C-EN-P - September 2008 73
DeviceNet Safety I/O for the GuardPLC Control System Chapter 6
Status Indicators
The DeviceNet safety I/O modules include status LED indicators.
Status LED Indicators
For details on status indicator operation, refer to the product
documentation for your specific module.
Status Data
In addition to input and output data, some DeviceNet safety I/O
modules support status data to monitor the I/O circuits. You can
create an application program to monitor these variables and take
appropriate action. Refer to your module’s product documentation.
Reaction Time
The input reaction time is the time from when an input signal is
changed to when network data is sent.
The output reaction time is the time from when a network signal is
received to when the state of output terminal is changed.
Some DeviceNet safety I/O modules may support ON-delay and
OFF-delay functions for input signals. You must include OFF-delay
times when calculating system reaction time.
See page 103 for information on calculating reaction times.
For information on determining the input and output reaction times,
refer to the product documentation for your specific DeviceNet safety
I/O module.
IMPORTANT
Status indicators are not reliable indicators for safety functions.
They should be used only for general diagnostics during
commissioning or troubleshooting. Do not attempt to use status
indicators as operational indicators.
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