OPC UA Connection Tag

Help Contents

Introduction

The OPC UA Connection Tag provides a connection to an external OPC UA Server. Fernhill SCADA uses this tag to work out how to connect to OPC UA Servers. The data in the external OPC UA Server can be read at a fixed interval, or on demand, or both.

Configuration Properties

The OPC UA Connection Tag supports the configuration properties of the Active Channel Tag plus these properties:

Property Type Version Description
ScanInterval TIME 3.69 The interval between each read. An interval value of zero (T#0s) disables periodic query execution. See Interval and Offset for information on how timed activities are scheduled.
ScanOffset TIME 3.69 The offset added to the ScanInterval to get the actual read time. See Interval and Offset for information on how timed activities are scheduled.
EndpointURL WSTRING 3.69 The Endpoint URL of the connection. This property must be a valid Uniform Resource Locator. For example:
opc.tcp://192.168.1.8:20296/
SecureChannelLifetime TIME 3.69 The requested lifetime of the security token of the communication channel. The actual lifetime of security token is negotiated with the OPC UA Server and may be different from the requested lifetime.
SecurityPolicy USINT 3.69 The security policy to use. Use one of these values to set the security policy:
  1. None
  2. Basic128Rsa15
  3. Basic256
  4. Basic256Sha256
  5. Aes128Sha256RsaOeap
  6. Aes256Sha256RsaPss
AuthenticationMethod USINT 3.69 How the OPC UA Connection authenticates with the OPC UA Server. Use one of these values to set the authentication method:
  1. Anonymous
  2. User Name & Password
UserName WSTRING 3.69 The user name to authenticate with the server.
Password WSTRING 3.69 The password used to authenticate with the server. Note: The password value is encrypted and not stored as plain text.

Dynamic Properties

The OPC UA Connection Tag supports the dynamic properties of the Active Channel Tag plus these properties:

Property Type Description
ScanTimer TimerStatus The status of the scan timer.
SecurityTokenTimer TimerStatus The status of the security token refresh timer.

Tag Commands

The OPC UA Connection Tag supports the tag commands of the Active Channel Tag, plus these tag commands:

Tag Command Version Description
Refresh 3.69 Requests an immediate read of all of the tags associated with this OPC UA Connection Tag.

Note: Event triggered data reads (from the Refresh Tag Command) and periodic data reads (defined by the ScanInterval property) are independent. You can use the Refresh Tag Command, or the ScanInterval property, or both to determine when the tags are read.

Relationships to Other Tag Types

The OPC UA Connection Tag builds on the features of these tag types:

Further Information

Interval and Offset

To learn how activities are scheduled using Interval and Offset.

I/O Analog Data Point Tag

To learn about the I/O Analog Data Point Tag that can be associated with the OPC Classic Connection Tag.

I/O Digital Data Point Tag

To learn about the I/O Digital Data Point Tag that can be associated with the OPC Classic Connection Tag.

I/O String Data Point Tag

To learn about the I/O String Data Point Tag that can be associated with the OPC Classic Connection Tag.

I/O Word Data Point Tag

To learn about the I/O Word Data Point Tag that can be associated with the OPC Classic Connection Tag.

I/O Double Word Data Point Tag

To learn about the I/O Double Word Data Point Tag that can be associated with the OPC Classic Connection Tag.

I/O Long Word Data Point Tag

To learn about the I/O Long Word Data Point Tag that can be associated with the OPC Classic Connection Tag.

OPC Client Driver

For an overview of the OPC Client Driver.

Glossary

For the meaning of terms used in Fernhill SCADA.