Subscription (FB)

FUNCTION_BLOCK PUBLIC ABSTRACT Subscription EXTENDS CBML.LConC IMPLEMENTS ISubscription, IOPCUAClientSubscriptionCallback

Basic function block to create subscriptions. A subscription contains an array of Items to subscribe.

Note

This kind of function block should be generated automatically by a configuration

Usage (Declaration):

{attribute 'no_assign'}
{attribute 'call_after_init'}
FUNCTION_BLOCK FINAL Subscription EXTENDS UA.Subscription
VAR CONSTANT
    lrInterval : LREAL := 500.0;
END_VAR
VAR
    _aItems : ARRAY[0..4] OF UA.Item := [
        (*  0 *) (eType:=UA.IEC_BYTE, psNodeId:=ADR('ns=4;s=path.byValue'), lrInterval:=lrInterval),
        (*  1 *) (eType:=UA.IEC_BOOL, psNodeId:=ADR('ns=4;s=path.xValue'), lrInterval:=lrInterval),
        (*  2 *) (eType:=UA.IEC_DATE, psNodeId:=ADR('ns=4;s=path.datValue'), lrInterval:=lrInterval),
        (*  3 *) (eType:=UA.IEC_DINT, psNodeId:=ADR('ns=4;s=path.diValue'), lrInterval:=lrInterval),
        (*  4 *) (eType:=UA.IEC_DATEANDTIME, psNodeId:=ADR('ns=4;s=path.dtValue'), lrInterval:=lrInterval),
    ];
END_VAR

Note

Don’t forget the SUPER^(); in the implementation part.

Override the Init method of UA.Subscription and set _pItem and _udiItemCount:

{attribute 'call_after_init'}
METHOD PROTECTED FINAL Init
    _pItem := ADR(_aItems);
    _udiItemCount := SIZEOF(_aItems) / SIZEOF(UA.Item);
    SUPER^.Init();

Implement the method PrepareValues of UA.Subscription:

METHOD PROTECTED FINAL PrepareValues : UA.ERROR
    (*  0 *) _aItems[0].pValue := ADR(byValue);
    (*  1 *) _aItems[1].pValue := ADR(xValue);
    (*  2 *) _aItems[2].pValue := ADR(datValue);
    (*  3 *) _aItems[3].pValue := ADR(diValue);
    (*  4 *) _aItems[4].pValue := ADR(dtValue);

Here an example of the call:

mySubscription : Subscription := (
    itfConnection:=_Connection,
    xPublishingEnabled := TRUE,
    lrPublishingInterval := 100,
    udiLifetimeCount := 150,
    udiMaxKeepAliveCount := 50,
    udiMaxNotificationsPerPublish := 100,
    byPriority := 0
);
InOut:

Scope

Name

Type

Initial

Comment

Inherited from

Input

xEnable

BOOL

LConC

Output

xBusy

BOOL

LConC

xError

BOOL

LConC

Input

itfConnection

IConnection

The connection of the UA.Client

xPublishingEnabled

BOOL

TRUE

Enables or disables the Subscription. TRUE: publishing is enabled for the Subscription. FALSE; publishing is disabled for the Subscription. The value of this parameter does not affect the value of the monitoring mode Attribute of MonitoredItems.

lrPublishingInterval

LREAL

This interval defines the cyclic rate that the Subscription is being requested to return Notifications to the Client. This interval is expressed in milliseconds.

udiLifetimeCount

UDINT

Requested lifetime count. The lifetime count shall be a minimum of three times the keep keep-alive count. When the publishing timer has expired this number of times without a Publish request being available to send a NotificationMessage, then the Subscription shall be deleted by the Server.

udiMaxKeepAliveCount

UDINT

Requested maximum keep-alive count. When the publishing timer has expired this number of times without requiring any NotificationMessage to be sent, the Subscription sends a keep-alive Message to the Client.

udiMaxNotificationsPerPublish

UDINT

The maximum number of notifications that the Client wishes to receive in a single Publish response. A value of zero indicates that there is no limit.

byPriority

BYTE

Indicates the relative priority of the Subscription. When more than one Subscription needs to send Notifications, the Server should de-queue a Publish request to the Subscription with the highest priority number. For Subscriptions with equal priority the Server should de-queue Publish requests in a round-robin fashion. A Client that does not require special priority settings should set this value to zero.

Output

xActive

BOOL

TRUE if the subscription is active.

eState

SUBSCRIPTION_STATE

The subscription state.

eErrorID

ERROR

Error code.

Methods:

Structure: