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9.3.3 Subscribing to Input Alarms
To subscribe to input state changes, that is, alarms, use the
Input_Get_Change X commands. All example control messages in this
chapter use the “term123” identifier string and the password property is set off
(see Table 9).
When you subscribe to this service, and an input state changes, you will
receive an alarm message. You can also subscribe to alarms on a continuous
basis, so that each time the state changes, you receive an alarm message until
you cancel the subscription with the Input_Change_Cancel command.
You can subscribe to alarms for all input state changes at once, or to each input
separately. Note that an input must be configured properly in order to get the
alarms. For more information about alarm configurations, see Chapter 5.4.
There are two ways to configure an analog input to operate with alarm sending
(see Chapter 5.4 for configurations):
• Alarming + Input High Limit + Input Low Limit + Sampling Interval
• Once/Continuously
An alarm from the analog pin is sent if the value is equal to or higher than the
high limit, or equal to or lower than the low limit. Define the frequency of the
state of the input polling in the sampling interval box (see Figure 7).
An alarm from the digital pin is sent if the digital pin state is changed and the
input state change is subscribed to that pin by the Input_Get_Change X
command.
Important: The latest subscription overrides any previous alarm subscription. The
alarm will only be sent as a response to the latest subscription; the originator of the
previous subscription will not be notified.
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