[HOLD_R] Hold real value

Function block HOLD_R switches the present or a saved input value to the output.

HOLD_R holds the last value on output [Out], if input [Hld] has value 1. If [Hld] has value 0, the present value of input [In] is provided at output [Out].

Pins

Input

Description

Data type

Default value
Value range

In

Input

Real

0.0

Hld

Hold

Boolean

0

0 - Hold is inactive.
1 - Hold is active.

TshVal

Threshold value

Configured value to control function block write attempts. An attempt is permissible only if the change of value is greater than or equal to [TshVal].

Note
Cannot be set to 0.0.

Real

0.1

Pers

Persistent

Boolean

0

0 - No
1 - Yes: the values are stored persistently.

BaObjRef

BA-Object reference
Link between function block and BACnet object.

Structure

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BaObjRef
> DeviceID

Device identifier
[DeviceID] includes object type and object instance in one ID.
Identifies the device object: local or remote. A local device object can also be identified by value 16#3FFFFF.

Double Word

16#3FFFFF

BaObjRef
> ObjectID

Object identifier
[ObjectID] includes object type and object instance in one ID.
Identifies the object on a device.

Double Word

16#3FFFFF

BaObjRef
> ItemID

Item identifier
[ItemID] represents an index in a view node object that references the BACnet object.
[ObjectID] and [ItemID] together define an indirect reference to the BACnet object.
Value -1 indicates a direct interface.

Integer

-1

 

Output

Description

Data type

Default value
Value range

Out

Output

Real

0.0

Dstb

Disturbed

Boolean

0

0 - Success reading persistent values.
1 - Error reading persistent values.

ErrCode

Error code indication

Integer

0: No error

= 0 - No error
> 0 - Error codes

Process response

At start up, HOLD_R holds the persistent value from the BACnet object. If [Hld] = 1, the read-out persistent value is set and held on output [Out]. If [Pers] = 0 or an access error, output [Out] is set with the input value [In] from the first processed cycle.

The persistent value must be available on the associated BACnet object as an extension property ('Extension by persistence' = 'Hold real number')

Application example

HOLD_R is used if input values are saved for processing acquired at a later date. For example, to hold a measured value or calculated setpoint.