OPC Classic Server Source block

The OPC Classic Server Source block makes OPC Classic items in the Architect OPC Classic Server available as fields in a Blueprint.

Note that this connector may or may not be available on the user palette, according to your license type.

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OPC Classic Server Source block

Description

The data of an OPC Classic server is identified by means of OPC Classic item identities (IDs). Each OPC Classic server vendor must provide a mechanism external to the OPC Classic specification to define items in the OPC Classic server. Architect uses the OPC Classic Server Source and Sink blocks to make items available in the OPC Classic server. (These two blocks are the only two in an Architect blueprint to which you can publish tags.)

NOTE: The OPC Classic Server Source blocks makes OPC Classic items available that are readable and writable, while the OPC Classic items of a OPC Classic Server Sink block are only readable.

DIAGRAM SHOWING THE OPC CLASSIC SERVER SOURCE

Block Type

Input/Output

Input/Output ports

The text source has no input ports and one output port. The fields in the output port can be of any type.

Functions performed on tags

The block updates the fields in the output port when a value is written to the OPC Classic item. The block performs no operations on the fields when it executes. When the blueprint is started the output fields are made available as OPC Classic items in the OPC Classic server. Not only are the fields made available in the OPC Classic server as OPC Classic items but the block also creates an OPC Classic public group in the server. The public group contains all the fields in the port. OPC Classic clients that can work with OPC Classic public groups can quickly be configured by connecting directly to the public group. The name of the public group is entered in the block's user interface.

The OPC Classic item id of an output field is as follows:

IO/groupname/fieldname

IO/ is a fix part
groupname is configured through the block's user interface
fieldname is the name of the output field that is also configured through the block's user interface

Execute mode

The block has 2 execute modes: Periodical and Execute Once. These modes determine when the block and the dataflow following the source will be executed.

Periodical will execute the block and the dataflow at the execute period specified in the block’s user interface
Execute Once will execute the block and the dataflow only once. In this mode the block may be used as a mechanism to change parameters in a blueprint while it is running.

Note:The value, timestamp and quality of output fields will be updated irrespective of the execute mode. These changes are made when the OPC Classic items are changed through the OPC Classic server.

Timestamp mode

The timestamp mode determines the timestamp of the output fields. The two options for timestamp mode are On Every Execute and On Data Received.

On Every Execute will set the timestamp of every field in the output port to the current execute time.
On Data Received will set the timestamp to the execute time. Only the OPC Classic items that were modified since the previous execute will have their timestamps changed. OPC Classic items that were not modified will keep their old timestamps.

Note: The timestamp mode can only be specified in the periodical execute mode. In Execute Once mode the timestamps are set to the execute time of the next source in the blueprint. In Execute Once mode only the timestamps of OPC Classic items that are modified will be changed.

Example

An OPC Classic server source with the group name configured as "Flow xyz" and output fields SetPoint, HiLimit and LowLimit will create the following OPC Classic elements:

OPC Classic Item ids
- IO/Flow xyz/SetPoint
- IO/Flow xyz/HiLimit
- IO/Flow xyz/LoLimit
Public Groups
- Flow xyz
Public Group Items
- SetPoint
- HiLimit
- LowLimit

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