Handshake Processor

The “Handshake Processor” is installed with the UA Office Link Application. The processor controls data flow based on a trigger and handshake condition. Data is passed through to the next stage only when the trigger value is “set”; a handshake with the control program needs to be performed before the next set of data is processed, according to the following state table (here, boolean values are expressed as 0 = false and 1 = true).

Trigger
Item
Handshake
Item
Control Program
Action
Handshake Processor
Action
0

0

Control program may
set trigger
Wait for trigger item
to become set
1

0

Wait for handshake item
to become set
Process current data set and
set handshake item
1

1

Reset trigger item

Wait for trigger item
to become reset
0

1

Wait for handshake item
to become reset
Reset handshake item

Data is only passed through if the trigger value is of “good” quality.

Trigger Item Data Type

The trigger item can be of any scalar type and is converted to ‘Boolean’ before evaluating the ‘set’ state. Boolean trigger items are considered ‘set’ when their value is ‘true’, numerical trigger items are considered ‘set’ when their value is not equal to zero, and string-typed trigger items are considered ‘set’ when the string is not empty.

Handshake Item Data Type

Handshake items are written as boolean values ‘true’ or ‘false’. If the target tag requires a different type and type conversion is either implicit or can be configured (see, for example, the OPC UA connector), then a target tag of a different type may be used.

Add to Task

Add the “Handshake Processor” to a task by dragging it from the “Build” panel onto the task’s “Task Builder” panel.

../_images/processor-handshake.png

Configuration

Select the “Handshake Processor” item in the “Task Builder” panel to view it’s properties.

../_images/processor-handshake-edit.png

You can change the following properties:

  • Topic
    The title of the “Handshake Processor” as it appears within the task builder.

Note that the trigger item is evaluated whenever its value changes.

Example 1

The following example shows a task that transfers data from OPC UA to an ODBC database. In this example, a single OPC UA topic “HandshakeTest” is used that contains the trigger item, the writable handshake item and the data that is to be transferred. When the trigger item becomes set, then data items are written to the ODBC database and the handshake item value (according to the handshake states table) is written to the handshake item within the “HandshakeTest” topic.

../_images/processor-handshake-example.png

Example 2

In this example, a separate, writable handshake OPC UA topic is used, containing the handshake item only. The functionality is otherwise the same as in Example 1.

../_images/processor-handshake-example2.png

Note

The examples above use an “Auto” ODBC topic and will attempt to write to database table “U_Handshake”. Rename the output topic name in the ODBC connector output to use a different table. Please see the task item notes for further information.