WP_REAL: Write real property

WP_REAL writes to a specified, writable property or array element of datatype Real in the data point. Attempts to write to a read-only property or array element will result in a rejected write and an error message.

Compatible data points:

Any BACnet data point with a writable property or array element of datatype Real.

Refer to data point objects for a detailed description of the BACnet data points.

Pin description (inputs)

BaObjRef
BA-Object reference Structure [BaObjRef] defines a bound connection between XFB and BACnet object. The binding occurs automatically. Manual configuration attempts are not necessary and can result in system errors.
DeviceId	Device identifier Double word (default value: 16#3FFFFF) [DeviceId] comprises object type and object instance in a single identifier. It is used to identify device object: local or remote. Local device object could also be identified by value 16#3FFFFF.
ObjectId	Object identifier Double word (default value: 16#3FFFFF) [ObjectId] comprises object type and object instance in a single identifier. It is used to identify object within a device.
ItemId	Item identifier Integer (default value: -1) [ItemId] represents an item index in the functional view node object, which references the BACnet object. [ObjectId] and [ItemId] together define an indirect access reference to the BACnet object. Value -1 indicates that direct binding is used.

TshVal
Threshold value Real (default value: 0.1) A parameterized value used to control the XFB write attempts. An attempt is only allowed if the value difference is equal or greater than [TshVal]. Note [TshVal] must not be set to 0.0.

TshVal

Threshold value

Real (default value: 0.1)

A parameterized value used to control the XFB write attempts. An attempt is only allowed if the value difference is equal or greater than [TshVal].

Note
[TshVal] must not be set to 0.0.

Val
Value Real (default value: 0.0) A calculated value (or a fixed value, that can be set for design needs) assigned by the Control program to update the property or array element. [Val] will be written if: [EnWrit] is True and [Val] changes by an amount equal or greater than [TshVal]. [EnWrit] changes from False to True. [RptWrit] and [EnWrit] are both True.

Val

Value

Real (default value: 0.0)

A calculated value (or a fixed value, that can be set for design needs) assigned by the Control program to update the property or array element.

[Val] will be written if:

[EnWrit] is True and [Val] changes by an amount equal or greater than [TshVal].
[EnWrit] changes from False to True.
[RptWrit] and [EnWrit] are both True.

RptWrit
Repeat write Boolean (default value: False) [RptWrit] forces a write of [Val] to the property or array element. The write operation is repeated with each program cycle for as long as [RptWrit] is True. [RptWrit] will typically be calculated and set by the control program. Note [RptWrit] must not be forced permanently to True by connecting to a block output that is always True. Doing so will cause a high level of communication traffic.
1 (True)	If [EnWrit] is True, [Val] is written to the property or array element with each program cycle for as long as [RptWrit] is True.
0 (False) default	No action.

RptWrit

Repeat write

Boolean (default value: False)

[RptWrit] forces a write of [Val] to the property or array element. The write operation is repeated with each program cycle for as long as [RptWrit] is True.

[RptWrit] will typically be calculated and set by the control program.

Note
[RptWrit] must not be forced permanently to True by connecting to a block output that is always True. Doing so will cause a high level of communication traffic.

1 (True)

If [EnWrit] is True, [Val] is written to the property or array element with each program cycle for as long as [RptWrit] is True.

0 (False)
default

No action.

EnWrit
Enable write Boolean (default value: True) When True, [EnWrit] enables values from inputs [Val] and [SetValid] to be written to the calculated value object. [Val] and [SetValid] will be written if: [EnWrit] changes from False to True.

EnWrit

Enable write

Boolean (default value: True)

When True, [EnWrit] enables values from inputs [Val] and [SetValid] to be written to the calculated value object.

[Val] and [SetValid] will be written if:

[EnWrit] changes from False to True.

PrpyId
Property identifier Integer (default value: 0) The parameterized BACnet Id number of the property being written. [PrpyId] can be set to any writeable property in the BACnet object.

PrpyId

Property identifier

Integer (default value: 0)

The parameterized BACnet Id number of the property being written.

[PrpyId] can be set to any writeable property in the BACnet object.

ArrayIdx
Array index Integer (default value: -1) Index number of the array element to be accessed by the XFB. [ArrayIdx] represents an optional parameterized input for specifying access to an element of a property of datatype BACnetARRAY or BACnetPriorityArray. [ArrayIdx] cannot be changed during runtime.
= -1 (default)	[ArrayIdx] not used.
= 0	(0) specifies the length of the array of the referenced property. Since it is not a function of the control program to write to this field, requests to [ArrayIdx] 0 will be rejected by the XFB.
> 0	Parameterized value.

Pin description (outputs)

WritVld
Write valid Boolean (default value: False) An indication of whether the last write attempt was successful. [WritVld] maintains the last write state (True or False) until reset by the next write attempt.
1 (True)	The last write attempt was successful.
0 (False)	The last write attempt was unsuccessful.

WritVld

Write valid

Boolean (default value: False)

An indication of whether the last write attempt was successful.

[WritVld] maintains the last write state (True or False) until reset by the next write attempt.

1 (True)

The last write attempt was successful.

0 (False)

The last write attempt was unsuccessful.

ErrCode
Error code indication Integer (default value: 20) The status of the last performance of the XFB read operation.
= 0	No error.
> 0	Error, see XFB error codes.

ErrCode

Error code indication

Integer (default value: 20)

The status of the last performance of the XFB read operation.

= 0

No error.

> 0

Error, see XFB error codes.

ErrWrit
Error while writing Integer (default value: 20) The status of the last execution of the XFB write operation.
= 0	No error.
> 0	Error, see XFB error codes.

ErrWrit

Error while writing

Integer (default value: 20)

The status of the last execution of the XFB write operation.

= 0

No error.

> 0

Error, see XFB error codes.

Use case examples

NOTICE

Note
Graphics reflect examples of XFB implementations; See ABT for current examples of CFC.

Due to graphical size limitations, function blocks may be missing or shown more closely grouped than is typical.