Object Dictionary 1
© May 1, 2001 Johnson Controls, Inc. www.johnsoncontrols.com
Code No. LIT-694080 Software Release 5.1
Analog Value/
BACnet
Analog Value
Introduction
Note: The Johnson Controls Analog Value object is considered a
BACnet™ Analog Value object, because it supports
BACnet functionality. In addition, this object has
Johnson Controls proprietary attributes.
Analog Value objects have similar software characteristics and
capabilities to N2 Analog Input objects; however, Analog Value
objects are not associated with any physical hardware and are the
result of a control process or operator entry. This object allows you to
hold an analog value for other objects to reference. For example, an
Interlock object can reference and base its operation on an analog
value such as Outdoor Air Temperature Low Limit. See the American
Society of Heating, Refrigerating and Air-Conditioning
Engineers, Inc. (ASHRAE) Standard 135-1995 for information on
this object and the BACnet communication standard.
Analog Value/BACnet Analog Value
2
Attributes
Specific Attributes
The attributes specific to the Analog Value object are listed in Table 1.
The Analog Value object also has the attributes of the
Metasys® Common object. Refer to Table 1 in the Metasys Common
Object chapter (LIT-694020) for details.
Table 1: Attribute Properties
Attribute Name Data Type N30
Flags*
M-Series
Flags*
N30 Default
Value
Options/Range
Metasys
Common
Attributes
See Table 1 in the
Metasys Common Object
chapter
(LIT-694020)
.
BACnet Required Attributes
Event State
Enumeration Normal Normal, Fault, Offnormal,
High-Limit, Low-Limit
Object Identifier
BACnet
Object ID
C
Out of Service
Boolean False Always False
Present Value
Float DNRW DNRW
Status Flags
Bit String False, False,
False, False
In Alarm, Fault,
Overridden, Out of
Service
See
BAC Status Flags
Enumeration Set in
Appendix A: Object
Enumeration Sets
(LIT-694980).
Units
Enumeration CW W Deg F
See
Units Enumeration
Set in Appendix A: Object
Enumeration Sets
(LIT-694980).
BACnet Optional Attributes
Acked
Transitions
1
Bit String True, True, True To-Offnormal, To-Fault,
To-Normal
See
BAC Event Bits
Enumeration Set
in
Appendix A: Object
Enumeration Sets
(LIT-694980).
COV Increment
2
Float CW W 0.1 Deg F Any value > 0
Continued on next page . . .
* C - Configurable, D - Default Attribute, N - Value Not Required, R - Association to Reliability, W - Writable
1 These attributes are required if the object supports intrinsic reporting.
2 This attribute is required if the object supports Change of Value (COV) reporting.
Object Dictionary
3
Attribute Name
(Cont.)
Data Type N30
Flags*
M-Series
Flags*
N30 Default
Value
Options/Range
BACnet Optional Attributes (Cont.)
Deadband
1
Float CW W 0.0
Event Enable
1
Bit String CW W True, True, True To-Offnormal, To-Fault,
To-Normal
See BAC Event Bits
Enumeration Set in
Appendix A: Object
Enumeration Sets
(LIT-694980).
Event Time
Stamps
1
Array NONE_FFFF BACnetArray[3] of BACnet
Time Stamp
High Limit
1
Float CW W 70.0
Limit Enable
1
Bit String CW W True, True Low Limit Enable, High
Limit Enable
See
BAC Limit Enable
Enumeration Set
in
Appendix A: Object
Enumeration Sets
(LIT-694980).
Low Limit
1
Float CW W 65.0
Notification
Class
1
Unsigned
Long
CW W 4194001 The BACnet Object
Identifier of the
Notification Class object
used for routing
Notify Type
1
Enumeration CW W Alarm Alarm, Event
See BAC Notify Type
Enumeration Set in
Appendix A: Object
Enumeration Sets
(LIT-694980).
Priority Array
Array
Profile Name
This BACnet optional attribute is not supported.
Reliability
Enumeration W W Reliable No Fault Detected
(Reliable), Over Range,
Under Range, Unreliable
Other
See Reliability
Enumeration Set in
Appendix A: Object
Enumeration Sets
(LIT-694980).
Relinquish
Default
Float CNW NW 0
Time Delay
1
Unsigned
Short
CW W 0 Units = seconds
Continued on next page . . .
* C - Configurable, N - Value Not Required, W - Writable
1 These attributes are required if the object supports intrinsic reporting.
Analog Value/BACnet Analog Value
4
Attribute Name
(Cont.)
Data Type N30
Flags*
M-Series
Flags*
N30 Default
Value
Options/Range
Johnson Controls Proprietary Attributes
Display
Precision
Enumeration CW W 10ths
See Display Precision
Enumeration Set in
Appendix A: Object
Enumeration Sets
(LIT-694980).
Intrinsic
Alarming
Boolean C False True, False
Max Value
Float CW W 1.7E38
Min Value
Float CW W -1.7E38
* C - Configurable, W - Writable
Object Dictionary
5
Attribute Definitions
Table 2 lists the definitions of the attributes specific to the Analog
Value object.
Table 2: Attribute Definitions
Attribute Name Definition
Metasys Common
Attributes
See Table 2 in the
Metasys Common Object
chapter
(LIT-694020)
.
BACnet Required Attributes
Event State
Indicates if an active event state associated with the object. If the object supports
intrinsic reporting, this attribute indicates the event state of the object. If not, the
attribute is Normal.
Object Identifier
Identifies the object with a unique numeric code.
Out of Service
Indicates the offline/online state of the connected hardware. The attribute exists for
compatibility with BACnet protocol and indicates whether the physical input that the
object represents is in service. When out of service, the object does not send
commands to the hardware. This attribute is always False due to the absence of
hardware.
Present Value
Indicates the current value of the analog value. Present Value is optionally
commandable. The optional Priority Array must be present for Present Value to be
commandable.
Status Flags
Contains four Boolean flags that indicate the general health of the object. Three of
the four flags are associated with the values of other attributes within the same
object. By reading these attributes, you can achieve a clearer picture of the object
status. The four flags are:
• In Alarm - In Alarm flag is False (0) if the Event State property value is
Normal; otherwise, the In Alarm flag is True (1).
• Fault - Fault flag is True (1) if the Reliability attribute is not reliable; otherwise,
the Fault flag is False (0).
• Overridden - Overridden flag is Logical 1 if the Present Value is decoupled
from the hardware output, because operator intervention provided a different
value.
•
Out of Service -
Out of Service flag is True if the Out of Service attribute
value is True; otherwise, the Out of Service flag is False.
Units
Indicates the increments of measure used by the object.
BACnet Optional Attributes
Acked Transitions
Conveys three flags that separately indicate the receipt of acknowledgements for
To-Offnormal, To-Fault, and To-Normal events. In Analog Value objects, transitions
to High Limit and Low Limit Event States are considered to be Offnormal events.
These flags clear upon the occurrence of the corresponding event and set under
any of these conditions:
upon receipt of the corresponding acknowledgement
upon the occurrence of the event if the corresponding flag is not set in the
Event Enable attribute (meaning event notifications are not generated for this
condition and, thus, no acknowledgement is expected)
upon the occurrence of the event if the corresponding flag is set in the Event
Enable attribute and the corresponding flag in the Ack Required attribute of the
Notification Class object implicitly referenced by the Notification Class attribute
of this object is not set (meaning no acknowledgement is expected)
This attribute is required if this object supports intrinsic reporting.
Continued on next page . . .
Analog Value/BACnet Analog Value
6
Attribute Name
(Cont.)
Definition
BACnet Optional Attributes (Cont.)
COV Increment
Specifies the minimum change in Present Value that sends a COV Notification to
subscriber COV clients. This attribute is required if the object supports COV
reporting.
Deadband
Specifies a range between the High Limit and Low Limit in which the Present Value
must remain for a To-Normal event to generate under these conditions:
The Present Value falls below the High Limit minus Deadband.
The Present Value exceeds the Low Limit plus the Deadband.
The Present Value remains within this range for a minimum period of time, as
specified in the Time Delay attribute.
Either the High Limit Enable or Low Limit Enable flag are set in the Limit
Enable attribute.
The To-Normal flag is set in the Event Enable attribute.
This attribute is required when the object supports intrinsic reporting.
Event Enable
Conveys three flags that separately enable and disable reporting of To-Offnormal,
To-Fault, and To-Normal events. In the context of Analog Value objects, transitions
to High Limit and Low Limit Event States are considered to be Offnormal events.
An unreliable condition generates a Fault event. This attribute is required if the
object supports intrinsic reporting.
Event Time Stamps
Conveys the times of the last To-Offnormal, To-Fault, and To-Normal event
notifications, respectively. Time or Date time stamps have FF in each octet.
Sequence time stamps are 0 if no event notification of that type has been
generated. This attribute is required if the object supports intrinsic reporting.
High Limit
Specifies a limit that the Present Value attribute must exceed before an event
generates. This attribute is required if the object supports intrinsic reporting.
A To-Offnormal event generates under these conditions:
The Present Value exceeds the High Limit for a minimum period of time,
specified in the Time Delay attribute.
The High Limit Enable flag is set in the Limit Enable attribute.
The To-Offnormal flag is set in the Event Enable attribute.
Once the Present Value exceeds the High Limit, the Present Value must fall below
the High Limit minus the Deadband before a To-Normal event generates under
these conditions:
The Present Value falls below the High Limit minus the Deadband for a
minimum period of time, specified in the Time Delay attribute.
The High Limit Enable flag is set in the Limit Enable attribute.
The To-Normal flag is set in the Event Enable attribute.
Limit Enable
Conveys two flags that separately enable and disable reporting of High Limit and
Low Limit Offnormal events and their return to Normal. This attribute is required if
the object supports intrinsic reporting.
Continued on next page . . .
Object Dictionary
7
Attribute Name
(Cont.)
Definition
BACnet Optional Attributes (Cont.)
Low Limit
Specifies a limit below which the Present Value attribute must fall before an event
generates. This attribute is required if the object supports intrinsic reporting.
A To-Offnormal event generates under these conditions:
The Present Value falls below the Low Limit for a minimum period of time,
specified in the Time Delay attribute.
The Low Limit Enable flag is set in the Limit Enable attribute.
The To-Offnormal flag is set in the Event Enable attribute.
Once the Present Value falls below the Low Limit, the Present Value must exceed
the Low Limit plus the Deadband before generating a To-Normal event under
these conditions:
The Present Value exceeds the Low Limit plus the Deadband for a minimum
period of time, specified in the Time Delay attribute.
The Low Limit Enable flag is set in the Limit Enable attribute.
The To-Normal flag is set in the Event Enable attribute.
Notification Class
Specifies the notification class used when handling and generating event
notifications for the object. This attribute implicitly refers to the Notification Class
object that has a Notification Class attribute of the same value. This attribute is
required if the object supports intrinsic reporting.
Notify Type
Conveys whether the notifications generated by the object are Events or Alarms.
This attribute is required if the object supports intrinsic reporting.
Priority Array
Contains prioritized commands in effect for the object. The highest priority
command is sent to the Present Value attribute.
Reliability
Sets the Reliability attribute to one of the following values when the Present Value
attribute is written:
• Reliable - Last value written to Present Value was between the Min Value and
Max Value limits.
• Unreliable High - Last value written to Present Value was greater than the Max
Value limit.
• Unreliable Low - Last value written to Present Value was less than the Min
Value limit.
In addition to the three values to which the Analog Value object can set the
Reliability attribute, any value defined in the
Metasys Common Object
(LIT-694020)
can be written directly to this attribute. Any value written to the
Reliability attribute remains until the next time the Present Value is written.
Relinquish Default
Indicates the default value used for the Present Value attribute when no
commands are currently controlling this object.
Time Delay
Specifies the minimum number of seconds that the Present Value must remain:
• outside the range defined by the High Limit and Low Limit attributes before a
To-Offnormal event generates
• within the range defined by the High Limit and Low Limit attributes, including
the Deadband attribute, before a To-Normal event generates
This attribute is required for intrinsic alarming.
Continued on next page . . .
Analog Value/BACnet Analog Value
8
Attribute Name
(Cont.)
Definition
Johnson Controls Proprietary Attributes
Display Precision
Indicates the rounded position and decimal places to display for this object.
Intrinsic Alarming
Enables the definition of the intrinsic alarm related attributes.
Max Value
Indicates the maximum reliable value for the Present Value attribute.
Min Value
Indicates the minimum reliable value for the Present Value attribute.
Commands
The Analog Value object supports the commands listed in Table 3.
The order of the commands in the table reflects how the commands
appear on the user interface.
Table 3: Supported Commands
Command Name Parameters Access Level Description
Adjust
The value to be
written to the
Present Value
attribute. This
parameter has a
Float data type.
Operate Releases Command Priorities 9
through 15 (Scheduling) and then writes
to the Present Value at the Default (16)
command priority.
Override
The value to be
written to the
Present Value
attribute. This
parameter has a
Float data type.
Supervise Updates the Present Value at Command
Priority Operator Override.
Override Release
Supervise Releases Command Priority Operator
Override from Present Value.
Release
1. Attribute name
2. Command priority
Modify Releases the identified command priority
from the specified, writable attribute, and
allows it to be controlled by the next
highest priority.
Release All
Attribute name Modify Releases Command Priorities 3
through 15 from the specified, writable
attribute.
Command Priorities 1 and 2 remain.
Enable
Modify Allows distribution of Changes-of-Value
and commanding.
Disable
Modify Prevents distribution of Changes-of-Value
and commanding.
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