OPC Unified Architecture Data Access Client communication protocol

Protocol specification
Basic concepts
Initiation of communication
Communication line configuration
Protocol configuration on the communication line
Protocol configuration on the communication station
I/O tag configuration
Browser dialog window
Tell commands
Literature
Changes and modifications
Document revisions

Kotva
popis_protokolu
popis_protokolu
Protocol specification

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The OPC UA protocol is the next generation of the OPC standard, which provides a cohesive, secure, and reliable platform-independent framework for access to the real-time data. The main difference in comparison with the previous versions is that the interprocess communication uses TCP/IP communication instead of COM/DCOM technology and therefore is OS (Windows) independent. This protocol supports two methods of data encoding (binary and XML). The existing OPC client implementation supports only binary encoding.

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Kotva

	endpoint
	endpoint

Endpoint: a physical address on a network, which allows the client to access to one or more of the services provided by the server.

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Kotva

	session
	session

Session: it is an abstract connection of the OPC UA server and a client on the OSI application layer.

Kotva

	monitoreditem
	monitoreditem

Monitored item: an entity on the OPC UA server that is defined by the client. It is used for monitoring the values.

...

Kotva

	subscription
	subscription

Subscription: an object on the OPC UA server that is defined by the client. It returns the notifications about the change of monitored items.

Kotva
inicializacia_komunikacie
inicializacia_komunikacie
Initiation of communication

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When initiating the communication, the client exchanges multiple messages with the server. In the case of binary encoding, "Hello Message" isthe first message sent from the client to the server. The message defines the size of receiving and sending buffers and the maximum size of messages that may be exchanged during TCP communication between client and server. It also defines the URL address of the endpoint. The server answers by sending sending an "Acknowledge message", in which it confirms the suggested parameters or modifies them according to its their limits.

Next The next message sent by the client is "OpenSecureChannel message". It is used to establish the a communication channel to exchange data. In this message, the client and server agree on what type of encrypting and signing mode will be used (either "sign and encrypt" or "encrypt" only). OPCUA client in D2000 System supports only unencrypted mode.

After establishing the communication channel, the client can send the message to create a session, "CreateSession Message". It is the connection on the OSI application layer. After the server confirms the request, the session must be activated by "ActivateSession Message". In this message, the client and server will agree on the algorithm for signing and encrypting if this mode has been agreed on when establishing the communication channel.

After activating the session, all types of messages that are intended for object management in the address space of the OPC UA server can be swapped. In this step, the client creates a subscriptions subscription with the parameters set on the communication station level for all stations within the communication line.

The monitored items should be then inserted to into these subscriptions. They correspond with the instances of I/O tags, which contain the parameters defined in the address dialog window.

From this moment, the server informs the client about the changes on in the monitored objects by

Kotva

	publish_message
	publish_message

"Publish message" in the periodic intervals (that have been set in the parameters of subscription). If the monitored objects have not been changed, the server will send a "Publish message" once in (Max KeepAlive Count * Publishing Interval) seconds. The message informs the client that the subscription is still active. A similar check mechanism is also on the client-side - it will send send a "Publish messagerequest" once every (Max KeepAlive Count * Publishing Interval). If the client does not send the acknowledgement acknowledgment "Publish message" within (LifeTime Count * Publishing Interval), the subscription will expire on the side of the server side.
OPC UA communication was tested with:
Simatic S-7 OPC UA Server
Bernecker PLC embedded OPC UA Server
Zenon OPC UA Server
Kotva
Kotva
komunikacna_linka komunikacna_linka
komunikacna_linka
Communication line configuration
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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").
TCP port: TCP port of OPC UA server (e.g. 4840).
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)
Encoding type: Type of encoding that is used for data exchange (currently only Binary encoding is supported).
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snsnSession NameRequested Channel LifetimeThe channel must be reopened before this time limit elapses. If the time is exceeded, the channel will be closed and unable to change data.Debug ModeDebug Threads
Parameter name Meaning Unit Default value
Kotva
ct
ct
Session text identifier. Session identifier should be a unique within the client instance, making it possible to search problems faster in the client or server logs. String Kom process
Client Type
Type of used client (driver for OPC UA communication):
Default - an original implementation of OPC UA client. Supports authentication (parameter Authentication Type) of Anonymous/Username types only. It does not support message encryption or signing.
Secure - a new implementation of OPC UA client with security support. Supports advanced authentication, encryption, and message signing capabilities.
Default
Secure
Default
Kotva
sn
sn
Session Name
Session text identifier. Session identifier should be unique within the client instance, making it possible to search problems faster in the client or server logs. String Kom process
Kotva
cl
cl
Requested Channel Lifetime
The channel must be reopened before this time limit elapses. If the time is exceeded, the channel
Kotva
cl cl hh:mm:ss 01:00:00
Kotva
st
st
Requested Session Timeout
Any message should be changed between client and server before this time limit elapses. If it is not sent, the sources within the session that are kept on the server are released. The primary work of this parameter is to remove the sessions that became inactive because of some unexpected reason. mm:ss 01:00
Kotva
at
at
Authentication Type
Type of autentication authentication used with the OPC UA server. Supported types are:
Anonymous: logon is anonymous
Username: logon uses user name and password
Certificate: logon uses x509 certificate (only for Client Type = Secure)
Anonymous / Username Anonymous
Kotva
tun
tun
Token User Name
User If Authentication type = Username, then user name used in the authentication if .
If Authentication type = Username. Certificate, then path to user certificate (e.g. D:\user_cert.der).

Kotva
pwd
pwd
Token Password
Password If Authentication type = Username, then password used in the authentication if .
If Authentication type = Username.
Kotva
dm dm It changes the number of information about the communication. We recommend to enable the mode Extended/Full only when detecting the problems and debugging the communication. Normal/Extended/Full Normal
Kotva
dt dt Parameter defines the thread(s) that will send the debug info about the communication. Receiving/Sending/Others treads/All threads All threads
...
Certificate, then path to user private key (e.g. D:\user_private_key.pem).

Kotva
sp
sp
Security Policy
Security policy (only for Client Type = Secure; for Client Type = Default a security policy None is used):
None - security policy None
Basic128Rsa15 - security policy Basic128Rsa15 (considered to be obsolete due to using a weak SHA-1 hashing algorithm)
Basic256 - security policy Basic256 (considered to be obsolete due to using a weak SHA-1 hashing algorithm)
Basic256Sha256 - security policy Basic256Sha256
Aes128Sha256RsaOaep - security policy Aes128Sha256RsaOaep
Aes256Sha256RsaPss - security policy Aes256Sha256RsaPss
None
Basic128Rsa15
Basic256
Basic256Sha256
Aes128Sha256RsaOaep
Aes256Sha256RsaPss None
Kotva
sm
sm
SecurityMode
A mode of message security in OPC UA communication (only for Client Type = Secure; for Client Type = Default a mode of message security None is used):
None - messages are not secured
Sign - messages are signed (protected against modification, but not against eavesdropping)
Sign & Encrypt- messages are signed and encrypted (protected both against modification and eavesdropping)
None
Sign
Sign & Encrypt None
Kotva
ppi
ppi
Preferred Policy Id
Identifier of preferred Security Policy (only for Client Type = Default for password encryption). If the OPC UA offers several security policies, it is possible to select a specific one according to the identifier sent by the OPC server (the identifier can be found from the logs). Examples of an identifier (text form is in parentheses):
PolicyId: 30 (0)
PolicyId: 31 (1)
PolicyId: 75 73 65 72 6E 61 6D 65 5F 62 61 73 69 63 31 32 38 52 73 61 31 35 (username_basic128Rsa15)
PolicyId: 75 73 65 72 6E 61 6D 65 5F 62 61 73 69 63 32 35 36 53 68 61 32 35 36 (username_basic256Sha256) - -
Kotva
rcd
rcd
Reconnect Delay
Waiting after the connection is broken before the connection is re-established. mm:ss.mss 00:10.000
Kotva
ecd
ecd
Error Connect Delay
Waiting after an unsuccessful connection attempt. mm:ss.mss 00:02.000
Kotva
dm
dm
Debug Mode
It changes the number of information about communication. We recommend enabling the Extended/Full modes only when detecting the problems and debugging the communication. The "Full + Trace (Secure only)" mode is valid only for Client Type = Secure. Normal/Extended/Full/
Full + Trace (Secure only) Normal
Kotva
dt
dt
Debug Threads
The parameter defines the thread(s) that will send the debug info about the communication. Receiving/Sending/Others treads/All threads All threads
Note: all X509 certificates used in OPC UA communication can be found in the following subdirectories of the kom-opcua directory in the application directory:
own - a directory with KOM process's own certificate (file cert.der). If this file does not exist, it is generated
Warning - this automatically generated certificate will only be valid for 1 year, so we recommend replacing it with a certificate valid for a longer period!
private - a directory with a private key for the KOM process own certificate (file private.pem)
rejected - a directory with rejected certificates
trusted - a directory with trusted certificates (the first time a connection is established to an OPC UA server, its certificate is stored in this directory)
Kotva
protokol_komunikacna_stanica
protokol_komunikacna_stanica
Protocol configuration on the communication station
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The parameters on the level of the communication station correspond with the setting of one subscription. It means the one communication station is equivalent to one instance of a subscription within the session.

Full name Description Unit Default value
Kotva
subrpi
subrpi
Requested Publishing Interval
Defines the time interval for the server to send the information about the change of monitored items within the instance subscription by "Publish message".
Note: This parameter defines a proposed value that the OPC UA server can change, e.g. Bernecker-Rainer always returned a value of "Publishing Interval" at least 50 ms, although the requested interval was smaller.
mi:ss.mss 00:05.000
Kotva
subrlc
subrlc
Requested LifeTime Count
If the client does not send the request for data till 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".
Note: This parameter defines a proposed value that the OPC UA server can change, e.g. Bernecker-Rainer always returned as a value of "LifeTime Count" a maximum of 600, although the requested value was greater.
Number 1000
Kotva
subrmkc
subrmkc
Requested Max KeepAlive Count
If the objects of 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.
Note: This parameter defines a proposed value that the OPC UA server can change, e.g. Bernecker-Rainer has always returned as a value of "Max KeepAlive Count" a maximum of 200, although the requested value was greater.
Number 5
Kotva
mnpp
mnpp
Max Notifications Per Publish
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
Kotva
pe
pe
Publishing Enabled
The parameter enables/disables the publishing within the subscription. YES/NO YES
Kotva
p
p
Priority
It defines a relative priority of a subscription. If the server should send more notifications, the subscription with higher priority is preferred. 0-255 0
Kotva
mqs
mqs
Samples Queue Size
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
Kotva
rt
rt
Read Timestamp
Timestamps used while reading a value:
None - timestamp received from OPC server is not used (value will be timestamped by the current time)
Source - SourceTimestamp is used
Server - ServerTimestamp is used (default)
- Server
Kotva
wt
wt
Write Timestamp
Timestamps used to write a value:
None - no timestamp is set
Source - SourceTimestamp is set (equal to the timestamp of written value)
Server - ServerTimestamp is set (equal to current time)
Both - both SourceTimestamp and ServerTimestamp are set
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
Kotva
wsc
wsc
Write Status Code
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
Kotva
wwa
wwa
Write Whole Array
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
Kotva
rm
rm
Read Mode
A way of reading values:
Subscribe: communication via subscriptions and notifications (standard)
Subscribe + Read: like Subscribe, in addition, periodic Read requests are sent (according to the time parameters of the station)
Read: send Read requests only
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
Kotva
nf
nf
No Filter
Ignoring filter parameters in the I/O tag configuration (Sampling type, DeadBand type, Trigger type).
In the specific case, the OPC UA server did not work correctly if monitored items with the specified filter parameters were inserted into the subscription.
YES/NO NO
Kotva
mpp
mpp
Max Pending Publish Requests
The maximum number of consecutive unconfirmed Publish requests (to which 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. -
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The parameters on the level of communication station correspond with the setting of one subscription. It means the one communication station is equivalent to one instance of subscription within session.
Requested Publishing IntervalRequested LifeTime CountRequested Max KeepAlive CountMax Notifications Per PublishPublishing EnabledPrioritySamples Queue SizeNumber
Full name Description Unit Default value
Kotva
subrpi subrpi
Defines the time interval for server to send the information about the change of monitored items within the instance subscription by "Publish message".
Note: This parameter defines a proposed value which the OPC UA server can change, e.g. Bernecker-Rainer always returned a value of "Publishing Interval" at least 50 ms, although the requested interval was smaller.
mi:ss.mss 00:05.000
Kotva
subrlc subrlc
If the client does not send the request for data till 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".
Note: This parameter defines a proposed value which the OPC UA server can change, e.g. Bernecker-Rainer always returned as a value of "LifeTime Count" a maximum of 600, although the requested value was greater.
Number 1000
Kotva
subrmkc subrmkc
If the objects of subscription are not changed, the server will send 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.
Note: This parameter defines a proposed value which the OPC UA server can change, e.g. Bernecker-Rainer has always returned as a value of "Max KeepAlive Count" a maximum of 200, although the requested value was greater.
Number 5
Kotva
mnpp mnpp 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
Kotva
pe pe Parameter enables/disables the publishing within the subscription. YES/NO 0
Kotva
p p It defines a relative priority of a subscription. If server should send more notifications, the subscription with higher priority is preferred. 0-255 0
Kotva
mqs mqs This parameter enables to create the object queue with the defined length on OPC UA server's side for each monitored item in subscription. 0

Kotva
protokol_merany_bod
protokol_merany_bod
I/O tag configuration
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Name Meaning Unit Default value
ID The identifier in text format, which is, in dependence on ID type, converted to the required native type.
Note: if an identifier %IGNORE is specified for ID type=String, the I/O tag is ignored. String
ID type Enumerated types of identifiers. They help to access to the objects in the objects in OPC UA address space.
Numeric-1B ID: Identifier limited to 1-byte value (0-255)
Numeric-2B ID: Identifier limited to 2-byte value (0-65535)
Numeric-4B ID: 4-byte identifier
String: Text identifier
Guid -16B ID: 16-byte (128-bit) number that is usually divided into four parts. For example 3F2504E0-4F89-11D3-9A0C-0305E82C3301.
ByteString: Identifier that is represented as a sequence of bytes. Numeric-1B ID / Numeric-2B ID/ Numeric-4B ID/String/Guid -16B ID/ByteString Undefined
Namespace
Kotva
namespace_index
namespace_index
Numerical identifier of name space the namespace of OPC UA server. Each OPC UA server can have N name spacesnamespaces. However, the object identifier must be unique in one name spacenamespace. Numeric
Variable type Value The value type of objects that can be processed by the OPC UA client. Variable type should be used only if the I/O tag is intended for writing. As regards the reading of the object value, the information about type is sent together with the value. Undefined / Boolean / Byte / SByte / Integer16 / Unsigned16 / Integer32 / Unsigned32 / Integer64 / Unsigned64 / Float / Double / String / UTC Time / Boolean array / Byte array / SByte array / Integer16 array / Unsigned16 array / Integer32 array / Unsigned32 array / Integer64 array / Unsigned64 array / Float array / Double array / String array / UTC Time array / LocalizedText / LocalizedText array Undefined
Array index If the object value is represented as a value array (Boolean array / Byte array / SByte array / Integer16 array / Unsigned16 array / Integer32 array / Unsigned32 array / Integer64 array / Unsigned64 array / Float array / Double array / String array / UTC Time array), the parameter defines its range or value of a particular item. The first element of array is identified by index 0.
A text representation of array index may be in several formats:
Separate integer, e.g. "6" or "0":- when you want to obtain only one a single value from the array.
Two integers separated by a colon, e.g. "6:7", - if you want to obtain the range of values.
The expression separated by a comma in the case of a multidimensional array, e.g. "6,7" - when you want to obtain the particular value of the item on of a 2D array. If you want to define the a range, you should use the expression expressions separated by semi-colona comma, e.g. "6:8,7:10".
String
"6:8,7:10".
Note: Writing is only supported for I/O tags with a specific index, not for ranges.
String
Write only It sets controls if the I/O tag is a part of the subscription. Its value will be sent periodically from the server in "Publish message". Unchecked/checked Unchecked
Expanded Node ID If it is checked, it enables to address addressing the ExpandedNodeId. Unlike the classic identifier in the OPC UA address space, ExpandedNodeId is supplemented by NameSpace URI and Server index.
Note: ExpandedNodeId is not yet supported in the KOM process. Unchecked/checked Unchecked
NamespaceUri Text identifier of name space the namespace of the OPC UA server that is used instead of the numerical representation of a namespace. String
ServerIndex Numerical A numerical identifier that address addresses the server number when using the ExpandedNodeID identifier. Numeric 0

Kotva
merany_bod_parametre
merany_bod_parametre
Settings of other parameters

Name Meaning Unit Default value
Sampling type Parameter The parameter defines a the sampling frequency of monitored objectthe monitored objects. When using the "Publishing rate", the frequency is equivalent to time 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 to specify the custom sampling interval, which may be defined in "Sampling Time". Publishing rate/Practical fastest rate/Custom rate Publishing rate
Sampling time Parameter 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 Data Change Notification, which is the part of Publish Message. When using "None", this band is ignored. Otherwise, there is used the relative or absolute value ("Percent"/"Absolute") from "DeadBand value". None/Absolute/Percent None
DeadBand value Parameter The parameter defines the custom value of a deadband if you chose the relative/absolute value ("Percent"/"Absolute").
0.0
Trigger type Parameter The parameter specifies the condition which causes Data Change Notification. When using "Status", only the status change is reported. Change of value and time stamp is timestamp are ignored. When using "Status,Value", the change of time stamp timestamp is ignored. "Status,Value,Timestamp" ensures the reporting in all options, i.e. when changing the status, value or time stamp.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
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This dialog window is intended for browsing and inserting the OPC UA objects into the address parameter of the I/O tag. The upper part contains the tree structure of the address space. When clicking on the object, the lower part of the window displays the direct descendants of the object (variables, tags).
Double click on one of the descendants transfers the address parameters of an object to the address dialog window of I/O tagthe I/O tag.
Note: Using Ctrl+C it is possible to copy a list of displayed descendants into the Windows clipboard. All descendants will be copied unless a specific descendant is selected.
Note: In versions from 17th December 2018 and newer, the recycling of browser dialog has been implemented. If the dialog is closed by the Close button or after selecting a tag, it is actually only hidden and it is available for browsing by another I/O tag within the same station so that the tree structure of the browsed objects is preserved. Clicking on the close icon at the top right corner will cause the dialog to be really closed.If the dialog is closed by the Close button or after selecting a tag, it is actually only hidden and it is available for browsing by another I/O tag within the same station so that the tree structure of the browsed objects is preserved. Clicking on the close icon at the top right corner will cause the dialog to be really closed.
Image Added
"Copy tags" button or a keyboard shortcut Ctrl+C copies the names of tags in a selected branch into the Windows clipboard. All tags will be copied unless a specific tag is selected.
"Copy tree" button or a keyboard shortcut Ctrl+Shift+C copies the names of tags and their addresses in all browsed branches into the Windows clipboard.Image Removed
Checking the "Structured tags" option causes the variables (tags) to appear in the tree structure in addition to the objects, and the KOM process also attempts to read their descendants descendants. This is useful for browsing OPC UA servers that support structured tags. You can also insert a tag into the address dialog window of the I/O tag by double-clicking the tag name in the tree structure.
Image RemovedImage Added
Kotva
tell_cmd
tell_cmd
Tell commands
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Command Syntax Meaning
STWATCH STWATCH StationName Tell command sends commands for the reading of values of all configured I/O tag

Kotva
literatura
literatura
Literature
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OPC Foundation manuals are placed on http://www.opcfoundation.org/.

OPC UA Part 1 - Overview and Concepts 1.01 Specification
OPC UA Part 2 - Security Model 1.01 Specification
OPC UA Part 3 - Address Space Model 1.01 Specification
OPC UA Part 4 - Services 1.01 Specification
OPC UA Part 5 - Information Model 1.01 Specification
OPC UA Part 6 - Mappings 1.00 Specification
OPC UA Part 7 - Profiles 1.00 Specification
OPC UA Part 8 - Data Access 1.01 Specification
...

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OPC Unified Architecture Data Access Client communication protocol

Kotva
popis_protokolu
popis_protokolu
Protocol specification

Kotva
inicializacia_komunikacie
inicializacia_komunikacie
Initiation of communication

Kotva
Kotva
komunikacna_linka komunikacna_linka
komunikacna_linka
Communication line configuration

Kotva
protokol_komunikacna_stanica
protokol_komunikacna_stanica
Protocol configuration on the communication station

Kotva
protokol_merany_bod
protokol_merany_bod
I/O tag configuration

Kotva
merany_bod_parametre
merany_bod_parametre
Settings of other parameters

Kotva
tell_cmd
tell_cmd
Tell commands

Kotva
literatura
literatura
Literature

Full name	Description	Unit	Default value
Kotva
subrpi	subrpi	Defines the time interval for server to send the information about the change of monitored items within the instance subscription by "Publish message". Note: This parameter defines a proposed value which the OPC UA server can change, e.g. Bernecker-Rainer always returned a value of "Publishing Interval" at least 50 ms, although the requested interval was smaller.	mi:ss.mss	00:05.000
Kotva
subrlc	subrlc	If the client does not send the request for data till 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". Note: This parameter defines a proposed value which the OPC UA server can change, e.g. Bernecker-Rainer always returned as a value of "LifeTime Count" a maximum of 600, although the requested value was greater.	Number	1000
Kotva
subrmkc	subrmkc	If the objects of subscription are not changed, the server will send 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. Note: This parameter defines a proposed value which the OPC UA server can change, e.g. Bernecker-Rainer has always returned as a value of "Max KeepAlive Count" a maximum of 200, although the requested value was greater.	Number	5
Kotva
mnpp	mnpp	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
Kotva
pe	pe	Parameter enables/disables the publishing within the subscription.	YES/NO	0
Kotva
p	p	It defines a relative priority of a subscription. If server should send more notifications, the subscription with higher priority is preferred.	0-255	0
Kotva
mqs	mqs	This parameter enables to create the object queue with the defined length on OPC UA server's side for each monitored item in subscription.		0

Name	Meaning	Unit	Default value
Sampling type	Parameter The parameter defines a the sampling frequency of monitored objectthe monitored objects. When using the "Publishing rate", the frequency is equivalent to time 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 to specify the custom sampling interval, which may be defined in "Sampling Time".	Publishing rate/Practical fastest rate/Custom rate	Publishing rate
Sampling time	Parameter 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 Data Change Notification, which is the part of Publish Message. When using "None", this band is ignored. Otherwise, there is used the relative or absolute value ("Percent"/"Absolute") from "DeadBand value".	None/Absolute/Percent	None
DeadBand value	Parameter The parameter defines the custom value of a deadband if you chose the relative/absolute value ("Percent"/"Absolute").		0.0
Trigger type	Parameter The parameter specifies the condition which causes Data Change Notification. When using "Status", only the status change is reported. Change of value and time stamp is timestamp are ignored. When using "Status,Value", the change of time stamp timestamp is ignored. "Status,Value,Timestamp" ensures the reporting in all options, i.e. when changing the status, value or time stamp.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

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OPC Unified Architecture Data Access Client communication protocol

Kotvapopis_protokolupopis_protokoluProtocol specification

Kotvainicializacia_komunikacieinicializacia_komunikacieInitiation of communication

Kotva Kotvakomunikacna_linkakomunikacna_linkakomunikacna_linkaCommunication line configuration

Kotvaprotokol_komunikacna_stanicaprotokol_komunikacna_stanicaProtocol configuration on the communication station

Kotvaprotokol_merany_bodprotokol_merany_bodI/O tag configuration

Kotvamerany_bod_parametremerany_bod_parametreSettings of other parameters

Kotvatell_cmdtell_cmdTell commands

KotvaliteraturaliteraturaLiterature

Kotva
popis_protokolu
popis_protokolu
Protocol specification

Kotva
inicializacia_komunikacie
inicializacia_komunikacie
Initiation of communication

Kotva
Kotva
komunikacna_linka komunikacna_linka
komunikacna_linka
Communication line configuration

Kotva
protokol_komunikacna_stanica
protokol_komunikacna_stanica
Protocol configuration on the communication station

Kotva
protokol_merany_bod
protokol_merany_bod
I/O tag configuration

Kotva
merany_bod_parametre
merany_bod_parametre
Settings of other parameters

Kotva
tell_cmd
tell_cmd
Tell commands

Kotva
literatura
literatura
Literature