User manual

Chapter Three Operation
man_905-105_2.9 Page 29
case, the output pulses are effectively 1 minute behind the input pulses. These update times may
be changed by the user. The pulse output update time should not be set to be more than the pulse
input update time. Note that the maximum pulse rate for both inputs and outputs is 100Hz.
As well as accumulating the pulse input, the module will also calculate the rate of pulses. Pulse rates
are treated as an “internal” analog input and are configured with analog sensitivities for change-of-state
transmissions. The maximum pulse rate corresponding to 20mA output may be configured by the user.
3.1.3 Analog Set-points
On “-1” modules, the “AI 1” input may be used to trigger the analog set-point status. High set point
and low set point levels are configurable. This set-point status turns ON when the analog 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 ”-2” modules, each analog input has set-point values for controlling digital outputs. The set-point
operation works as for the ”-1” module.
3.1.4 Start-up Poll
After a 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 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.
For a link with one or more repeaters, the internal CF status will only set for a failure between the
transmitting module (the source module) and the first repeater. If the communications failure occurs