Fieldbus
Communication
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195
BACnet/IP
WAGO-I/O-SYSTEM 750
BACnet/IP Controller
4.2.1.2.3 Services
BACnet is based on the Client-Server model. The Client makes requests to the
Server, which processes the Client's requests and returns a report.
Thirty-eight (38) standardized services are divided into 5 categories (Last up-
date: 2005)
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Alarms and events (Alarm and Event Services)
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Object access (Object Access Services)
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File access (File Access Services)
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Remote device access (Remote Device Management Service)
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Virtual terminal services (Virtual Terminal Service)
Alarms and events (Alarm and Event Services)
Responses to alarm and event reports can be one of three types
1. Change of Value Reporting (COV)
Data are only sent if they have been altered and the Client is registered for
COV Reporting in a COV Server.
2. Intrinsic Reporting
To send alarm or event reports to one or more recipients, the notification
and notification class are first sent to the Notification Class Object. This
object contains a list of those recipients that are registered for this notifica-
tion class and sends the report to these recipients.
3. Algorithmic Change Reporting
Algorithmic Change Reporting allows a BACnet device to have alarm and
event notifications available that are defined by the Event Enrollment Ob-
ject. It can be set for every property of every object. The same algorithms
apply as for Intrinsic Reporting, CHANGE_OF_BITSTRING,
CHANGE_OF_STATE, CHANGE_OF_VALUE,
COMMAND_FAILURE, FLOATING_LIMIT, OUT_OF_RANGE,
BEFFER_READY, CHANGE_OF_LIFE_SAFETY,
UNSIGNED_RANGE
The listed mechanisms can be used for the following alarm and event services
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AcknowledgeAlarm Service
To confirm an alarm report, it may be necessary for a person to implement
and confirm an alarm.
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ConfirmedCOVNotification Service
Informs subscribers of a change in property in a certain object. A confir-
mation is expected.
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UnconfirmedCOVNotification Service
Informs subscribers of changes in properties of a certain object. No con-
firmation is expected.
