Manual

WI-I/O 9-x Wireless Module User Manual v2.16
WI-I/O-EX-1-S-x Serial Module
Page 36
Fail-to-receive alarm. The second method is to set up a “comms OK” output using the “Reset
Outputs” function. The output is normally on, indicating “comms OK”, and will reset if the module
does not receive a message from the remote module within the configured reset time.
Consider a link between module #1 and #2, and assume that you want a “comms OK” output at #1. At
#2, map an unused input to an output at #1 such that the output is normally active (‘on”). If there is no
spare inputs at #2, you can use an internal input such as “low voltage status”. You will need to invert
the mappings such that the output is normally on (because the input is normally off).
At #1, configure a reset time for the output. The reset time should be greater than the update time for
the mapping at #2. If #1 fails to receive update messages from #2, then the output will reset,
indicating a communications failure. Notes regarding this method:
1. This method will work with repeaters in the link.
2. The “comms OK” output is fail-safe - if module #1 fails, then the output will reset indicating a
problem.
3. You should use separate outputs to indicate “comms OK” of different remote modules.
4. It is recommended that you set the reset time at #1 to more than twice the update time of the
mapping at #2. This means that the comms OK output will only reset if #1 misses two consecutive
updates from #2.
3.2.6 Testing and Commissioning
We recommend that you set-up and test the system with all of the modules together before you install
the modules. It is much easier to find a configuration problem.
When the system is configured, record the radio signal strength and background noise level for each
radio link. If there are future communications problems, you can compare the present measurements to
the as-commissioned values. This is an effective way of finding problems with antennas, cables and
also changes in the radio path (for example, the erection of new buildings).
3.3 Security Considerations
There are three dimensions of security considerations:
1. Failure to operate when required - or “operational reliability”.
The features discussed above optimize operating reliability. Using an acknowledgement and re-try
protocol ensures that the transmitting module is aware whether the transmitted message has been
transmitted reliably. The “fail to transmit” and “fail to receive” alarms provide indication if the
radio link has failed to operate.
2. Mal-operation, or operating when not requested.
This problem occurs when an output is “triggered” by the wrong radio device. The WI-I/O 9-x