Chapter Three
Operation
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corresponding to 20mA output may be configured by the user.
3.1.3
Analogue Set-points
On 105-1 modules, the “AI 1” input may be used to trigger the analogue set-point status.
High set point and low set point levels are configurable. This set-point status turns ON when
the analogue input moves below the low level, and turns OFF when it moves above the high
level. The high level must always be greater than, or equal to, the low level set point. This
set-point status may be mapped (inverted, if required) to any output in the network. The set-
point status is effectively an internal digital input.
On 105-2 modules, analogue inputs 1 - 4 have set-point values for controlling digital outputs.
The set-point operation works as for the 105-1 module.
3.1.4
Start-up Poll
After a 105 module has completed its initial diagnostics following power up, it will transmit
update messages to remote modules based on the values of the module’s inputs. The
module’s outputs will remain in the reset/off/zero condition until it receives update or
“change-of-state” messages from the remote modules.
The 105 module can transmit a special “start-up poll” message to another module. The
remote module will then immediately send update messages to this module such that its
outputs can be set to the correct value. Start-up polls will only occur if they are configured.
It is necessary to configure a start-up poll to each remote module which controls the module’s
outputs. For further information, refer to Chapter 4
Configuration
.
3.1.5
Communications Failure (CF)
The internal communications failure (CF) status is set if a module does not receive an
acknowledgement message after five attempts at transmitting a message. The CF status may
be configured to set a local digital output for an external alarm.
Although the CF status can set an output, it will not reset the output. That is, once
communications is re-established (and the CF status is reset), the output will stay “on”. The
Reset Output feature (see below) is used to reset the output.
The output will reset only when no communications failures occur within the configured
“Reset Output Time” for the output that CF status is mapped to. Note that if the reset output
time is not enabled, the CF status will remain set forever, once an unsuccessful transmission
occurs. See Chapter 4
Configuration
for further details.
3.1.6
Resetting Outputs
Each digital and analogue output may be individually configured to reset if that output has not
received a change-of-state or an update message within a certain time period. Generally this
time is set to twice the update period, so at least one update can be missed before an output is
reset.
In most cases it is desirable to reset outputs which are controlling equipment if there is a
system failure, however alarm or indication outputs are not reset so the last valid indication
remains shown. See Chapter 4
Configuration
for further details.
