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Communication line category: OPC UA Client
Host address: OPC UA server address. You may set the name according to UNC convention (e.g. "\\server" or "server", DNS names (e.g. "domain.com", "example.company.com") or IP address ("196.54.23.113"). In the case of redundant systems, multiple names/addresses separated by commas or semicolons can be entered.
The usage of the alternative path (the second or following name/address) is signalized by the FLB flag and a combination of FLN, FLO, FLP flags in the station value.
TCP port: TCP port of OPC UA server (e.g. 4840).
EndpointUrl: Endpoint address (e.g. opc.tcp://localhost:4840)
Note: when using the Client Type=Secure setting, neither Host address nor TCP port is used directly. However, if the string #HOST# is used within the EndpointUrl, it will be replaced by the IP addresses/names specified in the Host address parameter. This is useful when configuring a connection to a redundant OPC server that has multiple IP addresses/names.
Encoding type: Type of encoding that is used for data exchange (currently only Binary encoding is supported).
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Full name | Description | Unit | Default value | |||||||
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| Defines the time interval for the server to send the information about the change of monitored items within the instance subscription by "Publish message". | mi:ss.mss | 00:05.000 | |||||||
| If the client does not send the request for data by the time defined by (LifeTime Count * Publishing Interval), the subscription expires. The value should be minimally 3 times higher than the "Requested Max KeepAlive Count". | Number | 1000 | |||||||
| If the objects of the subscription are not changed, the server will send a keep-alive message after elapsing the time (Max Notifications Per Publish * Publishing Interval). The client will confirm this message when it sends a new request for data. | Number | 5 | |||||||
| The parameter defines the maximum number of notifications about the object change, which the server can send in one "Publish message". Zero indicates that the number of notifications is unlimited. | Number | 0 | |||||||
| The parameter enables/disables the publishing within the subscription. | YES/NO | YES | |||||||
| It defines the relative priority of a subscription. If the server should send more notifications, the subscription with higher priority is preferred. | 0-255 | 0 | |||||||
| This parameter enables creating an object queue with the defined length on the OPC UA server's side for each monitored item in a subscription. | Number | 0 | |||||||
| When the queue is full, the oldest values will be discarded (YES) or the newest values will be replaced (NO). | YES/NO | YES | |||||||
| Timestamps used while reading a value:
| - | Server | |||||||
| Timestamps used to write a value:
Note: If the OPC server does not support the writing of timestamps, according to the standard it should return the Bad_WriteNotSupported (2155020288) error code. | - | None | |||||||
| StatusCode item will be used when writing. Note: According to the standard, the OPC UA Wrapper returns the Bad_WriteNotSupported (2155020288) error code if the StatusCode entry is used when writing to the OPC DA Server version 2.05a. | YES/NO | YES | |||||||
| When an item of an array is written, the entire array is read first and then written. If this parameter is set to NO, only a specific array item is written, Note: According to the standard, if the OPC server does not support writing a specific array item, it should return the Bad_WriteNotSupported (2155020288) error code. Note: If this parameter is active, the "Write only" parameter must not be set at the I/O tag which addresses an item of the array. | YES/NO | NO | |||||||
| Values that are not older than the specified time interval (compared to the timestamp of the current value of the I/O tag) will be accepted. After writing, it may happen that the value read back is older (usually by several ms) compared to the time of writing unless the communication computer and the OPC UA server have exact time synchronization. Error messages may appear in the line log: | hh:mi:ss | 00:00:00 | |||||||
| A way of reading values:
Note: The Subscribe+Read and Read modes should only be used if there is a problem with standard communication, as they are less efficient and have a higher overhead. | Subscribe Subscribe+Read Read | Subscribe | |||||||
| Ignoring filter parameters in the I/O tag configuration (Sampling type, DeadBand type, Trigger type). | YES/NO | NO | |||||||
| The maximum number of consecutive unconfirmed Publish requests (to which the OPC UA server does not reply with a Publish Message), after which the connection will be closed. A value of 0 causes the connection to not be closed. Note: This parameter can be used to speed up the detection of a broken connection to the OPC UA server. | - | 0 |
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Name | Meaning | Unit | Default value |
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Sampling type | The parameter defines the sampling frequency of the monitored objects. When using the "Publishing rate", the frequency is equivalent to the Requested Publishing Interval, which is set on the communication station level. "Practical fastest rate" sets the sampling frequency on the maximum value. "Custom rate" enables the specification of a custom sampling interval, which may be defined in "Sampling Time". | Publishing rate/Practical fastest rate/Custom rate | Publishing rate |
Sampling time | The parameter allows you to set the custom sampling frequency if "Sampling type" is "Custom rate". | ss.ms | 0.0 |
DeadBand type | Deadband is a band in which the change of value does not cause a Data Change Notification, which is part of Publish Message. When using "None", this band is ignored. Otherwise, there is used the relative or absolute value ("Percent"/"Absolute") from the "DeadBand value". | None/Absolute/Percent | None |
DeadBand value | The parameter defines the custom value of a deadband if you chose the relative/absolute value ("Percent"/"Absolute"). | 0.0 | |
Trigger type | The parameter specifies the condition that causes Data Change Notification. When using "Status", only the status change is reported. Change of value and timestamp are ignored. When using "Status,Value", the change of timestamp is ignored. "Status,Value,Timestamp" ensures the reporting in all options, i.e. when changing the status, value, or timestamp. Note: a specific Simatic S7-1500 did not send value changes if this parameter was set to default "Status, Value, Timestamp" - changing it to "Status, Value" helped. | Status/Status,Value/Status,Value,Timestamp | Status,Value,Timestamp |
Note: in patches newer than 7/24/2024, conversion of Integer32 and Unsigned32 values to absolute time is supported. The integer value is understood as Epoch (Unix Timestamp - number of seconds from 1.1.1970), while in the Station configuration on the Time parameters tab it is possible to set whether it is the number of seconds from UTC time or from local time.
The protocol supports the configuration of the Destination tab of the I/O tag. If the value of the OPC item is of Array type, the communication protocol copies the values of the array, starting with the ArrayIndex item, into a column of a structured variable. The size of the structured variable is taken into consideration. If the number of structured variable rows is smaller than the VARIANT array, the values that are over the limit will be ignored.
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