WI-GTWY-9-xxx Wireless Gateway V1.18
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address goes into communications failure, then the remote address comms fail status is set ("on"
or 1) - every time an input with this remote address receives a radio message, then the remote
address comms fail status is reset ("off" or 0). While the remote address comms fail status is set,
the WI-GTWY-9-xxx disables any output messages being sent to this remote address.
When this feature is configured, all output transmissions are stopped if communications with a
remote module fails for a short period. They will start again when an input message from this
module is received. If the WI-GTWY-9-xxx determines that a output message should be sent to
an output which is disabled because of this feature, then the output message will not be sent and
the comms fail status of that output is set ("on" or 1).
If it is desired to use this function with a remote WI-I/O 9-x module, but there are no inputs from
this module being used, then it is easy to configure an unused input or an internal input (mains
fail or low battery voltage etc). It is the comms fail status for the input, which is used, not the
input itself.
2.6.1
Monitoring Communications Failure
The host device can monitor the communications status of an I/O point by reading the status
register for this point as a binary/discrete register. Modbus, and many other protocols, will
convert a 16 bit register value to a binary/discrete value by returning the most significant bit -
for the status register, this corresponds to the comms status bit.
For example, to monitor the comms status of I/O register 1045, perform a binary/discrete read on
register 6045 (the status register for 1045). A value of “1” will be returned if this I/O point is in
comms fail, and a “0” returned if the status is normal.
If it is desired to monitor the comms status of all I/O points, it is more efficient to only monitor
the comms status of one I/O point at each remote module (if this point is in comms fail, then all
points at the remote module will be in comms fail). If this point is an input, then the comms fail
time for this input can be made short, to give an early warning of a comms problem (this means
that the corresponding update time for the input at the WI-I/O 9-x will need to be short). If the
point is an output, then the update time for the output should be made short.
2.7
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 acknowledgment and
re-try protocol ensures that the transmitting module is aware whether the transmitted message
has been transmitted reliably. The “comms fail” 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-
GTWY-9-xxx modules use frequency encoding and a very secure addressing system to
