História stránky

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BACnet communication protocol (Building Automation and Control Networks) implements ANSI/ASHRAE 135-2001 standard.
This implementation was tested on with the following devices:

• Siemens
  • Desigo PXM20 (Control unit, LON interface, BACnet over LON)
  • Desigo PXC22 (Control station, LON interface, BACnet over LON)
  • Desigo PXC22-E.D (Control station, Ethernet interface, BACnet/IP)
  • Desigo PXG80-N (BACnet router, Ethernet interface, LON interface, BACnet/IP, BACnet over LON)
• Delta Controls
  • DSC-1212E (System controller, Ethernet interface, BACnet/IP)
  • DAC-633 (Application controller, MS/TP interface connected to DSC-1212E, which works as BACnet router)
  • DAC-633 (Application controller, MS/TP interface connected to the Moxa 5250 serial/ethernet converter and communicated directly as a BACnet MS/TP device in UDP mode)
  • DAC-1146 - (Application controller, MS/TP interface connected to DSC-1212E which works as BACnet router)
• Sauter
  • EYK220F001 (Automation station, Ethernet interface, BACnet/IP)
  • EYR203F001 (Universal controller connected to EYK220F001)
  • EYR207F001 (Universal controller connected to EYK220F001)
• York
  • BACnet MS/TP MicroGateway (Communication card for York coolers, RS485 interface, BACnet MS/TP)
• SE-Elektronic GmbH:
  • E-DDC3.1 (DDC automation station, Ethernet interface, BACnet/IP)
• Klimasoft
  • BACnet/Mbus converter MBG-MSTP: Converter from BACnet to Mbus protocol (RS485 interface, BACnet MS/TP)

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• Communication in Ethernet (BACnet/IP) and LONTalk networks.
• Limited support of MS/TP network (master-slave token-passing on RS-485): without automatic searching of for Master stations.
• Support of BACnet router (the connection between BACnet/IP and LONTalk networks).
• Reading and writing of simple values (binary, integer, real, strings, date, time, etc..) and any ASN sequences.
• Support of the polling method of data reading (messages ReadProperty-Request and ReadPropertyMultiple-Request messages)
• Support of change method of data reading (an optional registration by SubscribeCOV-Request or SubscribeCOVProperty-Request and following processing of ConfirmedCOVNotification-Request and UnconfirmedCOVNotification-Request).
• Writing the values by WriteProperty-Request.
• Dynamic change of I/O tag address by TELL command SETPTADDR (to read the values of Schedule objects).
• Work with objects of Schedule type (schedules).

BACnet protocol considers all the participants of the communication as the network devices. Each network device contains at least one (mostly just one) object Device (its Object Identifier must be unique within the whole network). This object contains other object objects of defined types (Analog Input, Analog Output, Analog Value, Binary Input, Binary Output, Binary Value, Calendar, Command, Event, Group, File, etc.). The object detection - see a description of Request type Who-Is and Who-Has Request types.
Each object has properties, which can be required mandatory or optional. Moreover, each producer of BACnet devices can implement other properties when necessary.
The messages in the BACnet protocol are related to the manipulation with of objects and their properties. They are defined with the help of ASN.1 (Abstract Syntax Notation version 1) and encoded by a simple version of BER (Basic Encoding Rules - encoding of ASN.1 messages).
The messages contain, besides fixed defined items, also items of 'Abstract Syntax & Notation' type. It means that any sequence (or "tree"), the meaning of which is defined by an implementer, can be in its place in the message. When using BER, it enables parsing of the message with the unknown items. BER defines two basic item types (tags): application and context.
The application tags are predefined:

• Null - empty value
• Boolean - yes/no
• Unsigned - positive integer
• Signed - integer
• Real - 4-byte real number
• Double- 8-byte real number
• Octet String - a sequence of character
• Character String - charset + text string
• Bit String - a sequence of bits
• Enumerated Value - enumerated value
• Date - date
• Time - time

• Kotva
  objectidentifier objectidentifier

  Object Identifier - identifier of the object (32-bit number, it consists of 10-bit number - Object Type and 22-bit number - Instance)

The context tags depend on the context (on the position in the message). Without knowing the context (a description of the message that is being parsed), it is possible to find out that the context tag No. 5 with the length of 4 bytes is on the particular position, but you need additional information whether the value is Unsigned, Signed, Real, Bitstring or a different type of value.
Besides the simple application and context tags, the properties may be also complex:

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Interpretation:
It is the Sequence of two tags: objectIdentifier is a contextual context tag with the number 0, of Object Identifier type. Its value is Object type=0 (analog input), Instance=10.
The tag listOfResults is a contextual context tag with number 1 and it is a Sequence of two tags. The first one is propertyIdentifier. It is a contextual context tag No. 2,  Enum type, value = 85 that corresponds to "present-value". A second tag is a contextual context one, No.4. It is a sequence that contains one Enumerated Value tag with the value=1 (application tag).
To parse this message, the D2000 KOM process must know ASN.1 definition of a message. Without it, the process can find out that the message contains the contextual context tag 2 (value=1 byte) but cannot know that it is Enumerated Value. It is not able to interpret this byte (it could be Enumerated Value, Unsigned or Signed number) and does not know that the name of this contextual context tag is propertyIdentifier and the value 85 corresponds to "present-value".

The properties of objects are mapped to I/O tags in the D2000 configuration. Due to the existence of contextual context tags, you may specify an Application tag in the I/O tag. It determines the interpretation of the contextual context tag. The parameter Complex address defines "a path" in the parse "tree" to get the values from the sequence that is defined by the implementer.

Kotva
komunikacna_linka komunikacna_linka

Communication line configuration

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• Communication line category: TCP/IP-UDP, LonWorks, Serial, SerialOverUDP Device Redundant.
• TCP/IP-UDP parameters:
  • Host: IP address or of the network interface that is used for communication by the D2000 KOM process process. A symbolic name that can be translated to an IP address can be entered too.
    Note: a symbolic name ALL can be entered - in which case all available interfaces are used.
  • Port: UDP port number that is used for communication by the D2000 KOM process  process (according to standard 0xBAC0, i.e. 47808).

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Keyword	Full name	Meaning	Unit	Default value
Kotva dbgi dbgi DBGI	Debug Input	Debug information about the input data. Meaning of the bits: 1. bit - debugging of  of ASN message parsing 2. bit - debugging of the I/O tag names that received a new value next higher bits - not used	-	0
Kotva dtq dtq DTQ	Debug Timeout Queue	Debug information about messages in time queue.	-	False
Kotva di di DI	Device Instance	Non-zero value causes that KOM process answers to Who-Is request by I-Am message. It contains a defined Device Instance. Zero value causes that Who-Is request is ignored.	-	0
Kotva rb rb RB	Receive Buffer	(for TCP/IP-UDP lines only) Size of the receive buffer which is set on configured for the UDP socket. Zero A zero value means the buffer size remains unchanged. 8192 bytes is a normal size in Windows. If there are more stations or more intensive communication, the buffer should be enhanced.	bytes	0
Kotva ro ro RO	Receive Only	If the value is True, no messages are sent to any station on the line. This parameter may be used when listening to the LonTalk communication: Configure the address, which is the same as the address of an existing LonTalk device, on the line. Also, configure the station with the device address which communication you need to listen to. The communication between devices is recorded to in the log file of the line. RO=True ensures that the KOM process does not influence the communication by its commands and responses.	-	False
Kotva sc sc SC	Send Count	(for LonWorks lines only) The retry count of one packet - default value is 1. However, in some situations when using iLON(tmTM) 10 Ethernet Adapter, the first message did not pass and the communication started to work correctly when SC=2. Note: Later we found out that this was caused because the Free topology bus had not been ended by a terminator. However, this parameter had been already implemented .	-	1
Kotva sd sd SD	Send Delay	(for LonWorks lines only) A complement to the SC parameter Send Count parameter that defines a delay (in ms) after each sending of the packet.	ms	0
Kotva vi vi VI	Vendor ID	Parameter Vendor ID of I-Am message (see the parameter Device Instance).	-	1

Line protocol parameters specific for BACnet MS/TP

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The communication station corresponds to a device on the BACnet network with which the KOM process communicates.

• Station type: BACnet/IP station must be configured on TCP/IP-UDP line. LonWorks station must be configured on the LonWorks line. MS/TP station must be configured on SerialOverUDP Device Redundant or Serial line.

• Kotva
  adresa adresa

  Address:
• BACnet/IP station: IP address of station (in the form A.B.C.D, e.g. 172.16.0.99)
• LonWorks station: address of LON subnet and LON node (in the form subnet.node, a subnet is an 8-bit number and a node is a 7-bit number)
• MS/TP station: number of the node on the line (0-254, address 255 is a broadcast)
• Port: (only for BACnet/IP): UDP port number on station (according to standard 0xBAC0, i.e. 47808)
• Domain: (only for LonWorks): 0 or 1, it relates with is related to the line configuration. On the LonWorks line you can configure , a membership to one or two domains can be configured. On BACnet station, if you choose some domain, it the selection of domain means that the device belongs to this domain (it influences 'domain' bit in LON address).
• Source network: source network number (i.e. a network with KOM process). This parameter may not be set for the LonWorks line. For TCP/IP-UDP line, it is a 16-bit number (or it is not set, see Note 2).

• Kotva
  destionation_network destionation_network

  Destination network: a 16-bit number of a destination network (i.e. a network including the device which communicates with the KOM process).
  Set this for the LonWorks line if the KOM process communicates with the device that is placed after located behind a BACnet router. In that case, the Address of the station is the address of the BACnet router and the Destination address is the address of the destination device.
  For TCP/IP-UDP line, use the Destination network if there  is used in a similar way if there is a communication between different BACnet networks.
  
  Note 1: This configuration was tested as follows:
  • Line: TCP/IP-UDP
  • Station type: BACnet/IP
  • Address: 172.16.99.1 (address of a BACnet router PXG80-N)
  • Destination network: 1
  • Destination address: 1.1 (address of PXC22 on a LON network after behind a BACnet router)
  The KOM process communicated with the PXC22 device PXC22 which was connected to a LON network by BACnet router via PXG80-N BACnet router. The KOM process communicates communicated with a BACnet router over Ethernet, so the line is TCP/IP-UDP. The communication between the BACnet router and the PXC22 station PXC22 was done performed over a LON network.
  
  

  Kotva
  pozn2 pozn2

  Note 2: We tested the a similar configuration. We used Delta Controls DSM-RTR (connected over Ethernet network) and a Klimasoft MBG device (a gateway on to M-Bus) after it connected over connected to Delta Controls via an MS/TP interface. The communication started only if only the Destination network (value 50020) and Destination address (value 96) were configured and not the Source network was not specified. However, in other another configuration, the communication proceeded worked also with the parameter Source networkthe Source network parameter specified. We recommend you to try various settings of network parameters for the devices.

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• Kotva
  destionation_address destionation_address

  Destination address: It is the address of the destination device if KOM communicates with it over the BACnet router. When setting this parameter, you can (but you may do not have to, see note about E-DDC3.1) set also the parameter Destination network. Parameter The Destination address should parameter should be in the form the subnet.node format (if the destination device is in on a LON network) or in the form A.B.C.D format (if the destination device is in on a BACnet/IP network).
  
  Note 1: On a BACnet/IP station you can configure the Destination address in the form subnet.node node format (e.g. 1.31). This configuration corresponds to the BACnet router, which communicates with the KOM process over BACnet/IP and is connected to the destination device over via a LONTalk network.
  
  Note 2: On BACnet/IP station you can configure the Destination address as a number from the interval 1-255. This configuration corresponds to the BACnet router, which communicates with the KOM process over BACnet/IP and is connected to the destination device by MS/TP bus (DAC-633).
  
  Note 3: On BACnet/IP station you can configure the Destination address as a bigger number (e.g. 2001), which works for E-DDC3.1.

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• Kotva
  resubscribe resubscribe

  Resubscribe interval: Time in seconds. After it elapses, a station again gets a request to send changes of I/O tags. This parameter relates to the I/O tags with the Request type that is equal to SubscribeCOV or SubscribeCOVProperty.
• Max APDU: Maximum size of the message (APDU = Application Protocol Data Unit) that is sent by the KOM process. A The default value is:
  • 1467 octets for TCP/IP-UDP line
  • 487 octets for SerialOverUDP Device Redundant or Serial lines (BACnet MS/TP)
  • 55 octets for LonWorks line (the
    
    The limitation depends on the size of packets which that may be transmitted over Ethernet and LonWorks. For LonWorks, the maximum value is 206. The value 55 is due to the limitation of the iLON 10 Ethernet adapter).
  
  The changing of the default value is important for testing and adjusting to complying with the stations which are able to process only smaller messages. For exampleCurrently, the reducing reduction of Max APDU influences only the size and amount of messages ReadPropertyMultiple-Request messages. These messages are intended for a periodic reading of I/O tag value (see I/O tag configuration).
  
  Note: The setting of Max APDU does not affect the size of max-APDU-length-accepted in APDU BACnet-Confirmed-Request-PDU, with the help by means of which the KOM process informs a partner what how big message messages it is capable to process. This parameter is configured by the station protocol parameter Segment-Response.
  
  
• Priority: A priority of a message in the BACnet protocol. There are 4 priorities: Normal (default), Urgent, CriticalEquipment, and LifeSafety.
• Rpt_timer & reply: (only for LonWorks) The parameters Repeat timer (default value = 1) and Retry (default value =1 ) of LonTalk protocol.
• Tx_timer: (only for LonWorks) Parameter Tx_timer in LonTalk protocol. Default value = 3.
• Timeout and retry: A timeout in milliseconds to confirm the message. Default The default value according to the BACnet protocol is 3000 ms. After the timeout elapses, the message is sent retry-times. If any confirmation is not received, an error count will increase on for the station.
  
  Note: When testing the Siemens PXC64-U device (the communication over LonTalk), we had to set Retry=8, Timeout=300 (more retries with shorter timeout). Due to that, we had to increase the values COM_ERR=10, HARD_ERR=20 so that the station did not switch to an error state at when retrying to send the message.
• COM_ERR: The value of error counter on for the station when the station switches to COM_ERR status. The situation when the station does not reply on call for reading or writing of value could be consider as to a read/write request is considered as an error. A negative confirmation of a command (refusal of recordingwriting) is not the an error. Default The default value = is 5. See the parameters Timeout and retry.
• HARD_ERR: The value of the error counter on for the station when the station switches to HARD_ERR status. Default The default value = is 10. See the parameters Timeout and retry.
• Register-Foreign-Device, R-F-D Time to live: In this example the station is placed on LONTalk network after BACnet router which communicates with , let's have a station located on a LONTalk network behind a BACnet router that communicates with the KOM process over Ethernet (e.g. Desigo PXG80-N). The BACnet router sends the broadcasts from LONTalk to Ethernet as UDP broadcasts. If distributing of UDP broadcasts is disabled or the KOM process is placed in other a different segment of the network than the BACnet router (so it does not receive any UDP broadcasts), you should mark off check the option Register-Foreign-Device on the station. This will cause, cause the KOM process will to send the message Register-Foreign-Device message to a BVLC router (BACnet Virtual Link Control) after the start. The message calls for the requests registration to the FDT table (Foreign Device Table) in the router. The router sends the broadcasts in the form of UDP unicast (whose distribution is not limited to one segment) to the devices that are registered in the FDT table. The TTL (time to live) - time in seconds (1-65535) is the parameter of message Register-Foreign-Device. It defines the expiration of registration that stops the sending of UDP unicasts. That is why the KOM process must ask BACNet the BACnet router to re-register it before TTL expires. If there are more stations after behind a BACnet router, just mark off check Register-Foreign-Device on one of them.
  
  Note 1: If the router does not support BBMD functionality (BACnet/IP Broadcast Management Device), it replies to the message Register-Foreign-Device message with the an error code and it does not send LonTalk broadcasts to the KOM process in the form of UDP unicasts. In that case, you must use other solution solutions (the communication over iLon Ethernet Adapter, the placing of the KOM process on the same segment in the network on which is the BACnet router is , etc.).
  Note 2: Router Desigo PXG80-N supports this functionality (tested). The control station Desigo PXC22-E.D does not support it probably (not tested yet).
  Note 3: In the case of Desigo devices, if the D2000 KOM process is on a different network segment than the Desigo device, this parameter must be checked at the station. Otherwie Otherwise, Who-Is and Who-Has queries requests won't work (and thus addressing by object's name), as responses to these queries requests are sent as UDP broadcasts which will not go through a router.
  
  
• Master: (only for MS/TP): The station is of Master type. The KOM process transmits a token to the Master station which has the next larger address than is the address of the KOM process (the parameter of line MS/TP address line parameter). If the addresses of all Master station stations are lower than addresses the address of the KOM process, the token is given to the Master station with the lowest address. If any no Master station has not been configured, the KOM process supposes to be the only master and does not give any pass the token. You should get the information about the type of station from a producer or device documentation.
  
  Note: The current version implementation of the BACnet protocol does not contain the automatic search of for the Master station. You can find more information in the section Comment on BACnet MS/TP implementation.

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Station protocol parameters

Kotva
merany_bod merany_bod

I/O tag configuration

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• Kotva
  requesttype requesttype

  Request type: Reading and writing of the object properties may be done in several ways:

  • Kotva
    readproperty readproperty

    ReadProperty - a periodical reading of object property as request-response. A polling period of polling is set configured on the tab Time parameters tab of station. The message ReadProperty-Request represents message is used for the request and the message the ReadProperty-Ack represents  message is the response from the device. The periodic reading loads burdens the network and is ineffective. That is why, if the device supports the sending of change data, we recommend you to use SubscribeCOV or SubscribeCOVProperty requests.
    The message The ReadProperty-Request message is sent if checkbox the Subscribe/read checkbox is ticked offchecked.
  • ReadPropertyMultiple - the functionality is similar to the previous parameter. Unlike ReadProperty, more object properties are sent in one request-/response, so the communication is much more effective. The message ReadPropertyMultiple-Requestrepresents the message is used for the request and the message the ReadPropertyMultiple-Ack represents message is the response from the device.
    The message The ReadPropertyMultiple-Request message is sent if checkbox the Subscribe/read checkbox is ticked offchecked.
  • WriteProperty - the message the WriteProperty-Request writes message is used for writing the values. The parameter Application tag parameter must be specified as well. If Subscribe/read is marked offchecked, the recorded written value is reread verified by reading from the station using the message ReadProperty-Request message after writing.

  • Kotva
    subscribecov subscribecov

    SubscribeCOV - activation of reading of object value by when they change method. If the checkbox the Subscribe/read checkbox is ticked offchecked, after starting, the KOM process send sends the message SubscribeCOV-Request message which asks the device to send information about the change of object value. You can specify whether the device will send the confirmed notifications (message ConfirmedCOVNotification-Request message) or the unconfirmed ones (UnconfirmedCOVNotification-Request). The confirmed notification requires the an explicit confirmation from the KOM (the message BACnet-SimpleACK-PDU message), so it loads puts more load on the network. However, the probability that the notification will be lost is lower than if you would specify the unconfirmed notification in case of using unconfirmed notifications (if the device does not receive the a confirmation, it repeats the message).
    
    Note 1: Besides the dynamic registration by the message SubscribeCOV-Request message, some devices can support also a static one (it is saved in the configuration). So the registration is not required and the checkbox Subscribe/read may not be ticked offleft unchecked.
    Note 2: The registration can be sent in at regular intervals (e.g. because of the a potential failure of the device power supply). You can set this interval on the station - the parameter Resubscribe interval parameter.

  • Kotva
    subscribecovproperty subscribecovproperty

    SubscribeCOVProperty - the functionality is similar to SubscribeCOV. Moreover, you can specify the Property identifier (so you can monitor also the changes of other object properties as valuesthan the present value) and Increment - a size of increment which causes the change will to be sent (i.e. a dead zoneband).
    This message - The SubscribeCOVProperty-Request message is sent.
    
    Note: The device Siemens PXC64-U device did not support the parameter Increment parameter.

  • Kotva
    whois whois

    WhoIs - the identification message Who-Is-Request to detect the type of Device Object in a device. The message The I-Am-Request message is the response (it contains the fields iAmDeviceIdentifier, maxAPDULengthAccepted, segmentationSupported, and vendorID fields). If the I/O tag is TxtI, this information is extracted to the value of the I/O tag in a text form. After you identify the Device Object, you can configure the I/O tag for reading the property object-list of this Device Object. If the device implements this property, it returns the list of identifiers of all objects which it contains. Then you can detect query the properties of these objects (object-name, location, description, present-value ..)
    
    Note: For Siemens PXC64-U you must set the Array index and then read the property object-list. Array index=0 defines the number of array elements, Array index=1 up to N enables the access to the individual elements.

  • Kotva
    whohas whohas

    WhoHas - the identification message Who-Has-Request to detect the object name from the object identifier or vice versa. The response is the message the I-Have-Request message (it contains the fields : deviceIdentifier, objectIdentifier, and objectName). The message The Who-Has-Request message is sent only once when initialization of I/O tag (or after the TELL command SETPTADDR). It is intended for the transfer between names and identifiers of objects.
    The message Who-Has-Request will contain either name or identifier of the object depending on whether the Address type has been configured as Name or Object type+Instance in I/O tag.
    If Subscribe/read is ticked offchecked, you can use the information from the BACnet cache, which is much more faster than detection from the communication.

  • Kotva
    readwritescheduler readwritescheduler

    ReadWriteScheduler - the message the ReadProperty-RequestnaRequest message is used for the request, the message WriteProperty-Request message is used for write (it writes N pairs time-valuevalue pairs). Th The configuration is used for the reading and writing of objects of schedule type, see the article the Scheduler in Siemens Desigo devices paragraph.

  • Kotva
    geteventinformation geteventinformation

    GetEventInformation: a detection of objects that are in alarm or error state or they need to be acknowledged, see the section Information about events.

  • Kotva
    acknowledgealarm acknowledgealarm

    AcknowledgeAlarm: the acknowledgement acknowledgment of alarms that have been loaded read by the GetEventInformation request GetEventInformation. See the section Information about alarms. I/O tag must be the text output (TxtO).

• Kotva
  addresstype addresstype

  Address type: Each object in the BACnet protocol is addressed by an Object identifier. When designing the application in the Desigo system, the objects are represented by a name, but the object address is not accessible and can vary following the changes of application. As regards On the other hand, the Delta Controls devices , they contain the objects whose addresses are defined by the author of the application. For this reason, there are two ways how to define the address of I/O tag which corresponds to two Address type:
  • Name: enter the object name. A type of object and number of instance are found out instance number is queried dynamically from the communication. To avoid the overloading of communication lines when starting the KOM process, data are is stored in a BACnet cache.
  • Object type + Instance: enter the type of object and an instance number of instance. This is recommended for BACnet objects with the constant addresses.
• Object type: type of objects, whose properties will be read/written. You can use the predefined types or write the number of a new type of object which has been defined by a producer. The type of object is a 10-bit number.
• Instance: a sequence an object identification number of object within the object type. Each object has a unique Object Identifier in the device, which is a pair [Object type, Instance].

• Kotva
  objectname objectname

  Object Name: name of the object, when Address type = Name, i.e. it means the I/O tag address [Object type, Instance], is detected dynamically from the communication. Object Name must be set without be specified exactly, i.e. spaces in the beginning and at the end are not tolerated, and the uppercase upper and lower case letters must correspond to the object name that is stored in the BACnet device with which it communicates.
• Property type: type of property - set only only PropertyIdentifier is specified for Simple, and both PropertyIdentifier and Complex address must be specified for Complex. The complex type of property is necessary when for the parsing by implementer of extension of the of OEM-extended standard messages (items of 'Abstract Syntax & Notation' type). When sending the messages ReadProperty-Request, ReadPropertyMultiple-Request, SubscribeCOV-Request, and  SubscribeCOVProperty-RequestRequest messages, the Complex address is ignored.
• Property identifier: identifier of an object property. You can use the predefined properties or number configure a numeric identifier of new property which has was defined by the producerOEM manufacturer. The type of property identifier is Enumerated Value, the properties 0-511 are reserved for BACnet, the numbers from 512 to 4194303 can be used for by the device producersOEM manufacturer.
• Array index: some properties may be defined as value array. The arrays of values. In this case, a particular item of an array can be read or written.

• Kotva
  application_tag application_tag

  Application tag: it must be specified when writing the value (Request type=WriteProperty) and possibly for other types of requests , if the parsed response contains the context tags which application type is unknown because it is the extension of messages defined by implementerthe OEM manufacturer. The exception is an output tag of text tag type that is considered to be 'AnyTree', as regards if the unspecified application tag is unspecified, and is it can be used to write any user-specified ASN sequence.
  
  Note: If the the value is Invalid, it is not written as the defined Application tag, but as Application tag "Null".

• Kotva
  complex_address complex_address

  Complex address: address of a tag in a 'tree' in connection with the extension of messages that have been defined by implementerthe OEM manufacturer.
  Example of address: [1].[3].2.1
  Description:
  [1] - context tag No.1 (it is assumed that it is the sequence),
  [3] - it is the context tag No. 2 3 in this sequence (again, it must be the a sequence),
  2 - it is the second tag in order in this sequence (again, it must be the a sequence),
  1 - it is the first tag in order in this sequence.
  The address in 'tree' starts from the propertyValue level propertyValue (see the examples below). The easiest way to view the parsed message is to turn on debugging for a debug on the line and watch the debug info on the console or in the line log of linefile.
  
  Example 1: There is Let's have a device that contains the object of type 2 (Analog Value) with the instance number 1. It is assumed Let's assume that the device sends the object value as a triplet of numbers. The first number is the current value, the second one is a one-minute average and the third one is a ten-minute average. The log of the parsed message could be the following:

   === ASN Body beg ===
   objectIdentifier (tag 0) OBJID 2 analog-value,1
   listOfResults (tag 1) SEQUENCE {
    propertyIdentifier (tag 2) ENUM 85 present-value
    propertyValue (tag 4) SEQUENCE {
     REAL 1.40000E+00
     REAL 1.10000E+00
     REAL 1.30000E+00
    }
   }
   === ASN Body end ===
  

  If you wants want all three values, you must configure three I/O tags (Object type=analog_value, Instance=1, Property-identifier=present-value, Property-type=complex), which differ in the complex address (for the first I/O tag = specify 1, for the second one = specify 2, and for the third one = one specify 3). Tick off the checkbox Subscribe/read only in one configuration  in a configuration of one of these I/O tags only, because the response to one request is the message with three values. When sending the messages ReadProperty-Request, ReadPropertyMultiple-Request, SubscribeCOV-Request, SubscribeCOVProperty-Request, and WriteProperty-Request messages, the complex address is not used.
  
  Note: If you configure the I/O tag with Property-type=simple, its value would be set on to the first found value after parsing of the message (see in the previous example , it is 1.40000E+00).
  
  Example 2: Siemens Desigo PXC64-U contains I/O tag (Object type=schedule, Instance=6, Subscribe-read is ticked offchecked, Property-identifier=weekly-schedule, Property-type=complex, Array index=1, Complex address=1). A debugging has been started on the line. After the I/O tag is saved, the KOM process sends the request and writes the response:

   === ASN Body beg ===
   objectIdentifier (tag 0) OBJID 17 schedule,6
   propertyIdentifier (tag 1) ENUM 123 weekly-schedule
   propertyArrayIndex (tag 2) UNSIGNED 1
   propertyValue (tag 3) SEQUENCE {
    SEQUENCE {
     TIME 0:0:0.0
     UNSIGNED 2
     TIME 4:0:0.0
     UNSIGNED 3
     TIME 22:0:0.0
     UNSIGNED 1
    }
   }
   === ASN Body end ===
  

  In propertyValue, there is the sequence of 6 values (time and positive number alternately). If you want to access to the first time, you have to set Complex address=1.1, if to the first positive number, set Complex address=1.2. I.e. the first element - sequence - the second element in the order within it (UNSIGNED 2). If you need to access to more times and/or values at the same time, you must configure several I/O tags and tick off check the checkbox Subscribe/read only checkbox in one of them only.
  
  Note 1: The value of If the I/O tag remains Unknown, after creating and saving it with the was created with a complex address 1, its value would remain Unknown, because this address matches with 1. the 1st element in propertyValue, which is the a sequence but , not a simple typtype.
  
  

  Kotva
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  Note 2: The I/O tag of Text type are is able to cover contain not only simple value but also any ASN sequence. The values are written according to rules for record writing of ASN sequence. If you set Complex address=1 and change the I/O tag to text input or text output in the previous example, its value will be a string " T0:0:0.0; u2; T4:0:0.0; u3; T22:0:0.0; u1; ". If Property-type=complex, but Complex address is not defined, a result is the value will be "0{ T0:0:0.0; u2; T4:0:0.0; u3; T22:0:0.0; u1; }".
• Increment: increment of value change in the object property which causes the reporting of a change (see SubscribeCOVProperty).
• Confirmed: if the checkbox is ticked, it  the checkbox specifies whether the device will should send the confirmed notifications (ConfirmedCOVNotification-Request) or unconfirmed one (UnconfirmedCOVNotification-Request) for the configured Request types SubscribeCOV and SubscribeCOVProperty.

• Kotva
  subscriberead subscriberead

  Subscribe/read: if the checkbox is ticked, the proper respective messages for reading/registration of value changes are sent for the configured Request types:
  ReadProperty: the message ReadProperty-Request message
  ReadPropertyMultiple: the message ReadPropertyMultiple-RequestRequest message
  SubscribeCOV: the message SubscribeCOV-RequestRequest message 
  SubscribeCOVProperty: the message SubscribeCOVProperty-Request message 
  ReadWriteScheduler: the message ReadProperty-RequestRequest message

• Period from: if the a nonzero value is set and the checkbox Subscribe/read checkbox is ticked, the messages Subscribe/read messages will not be sent in the interval Polling period, which has been configured on the station, but in the period defined period by this parameter (in seconds). In this way, you can configure various Polling polling periods for different objects on one station. Moreover, you can detect with the help of whether the station communicates, using one I/O tag with Request type ReadProperty and a small Period whether the station communicatesvalue of the Period parameter.
• Local time: if the checkbox is ticked, the recorded respectively read received/sent times and dates are considered to be in a local time. If not, otherwise they are in monotonous considered to be monotonic UTC time.
• Flags-to-flags: if the checkbox is ticked, it causes that besides of I/O tag value, its the user flags FA, FB, FC, FD are set to be set beside the I/O tag value, for the Request types SubscribeCOV and SubscribeCOVProperty Request types. The value of status-flags attribute (of BACnetStatusFlags type) is mapped to these flags, if they are it is sent. BACnetStatusFlags is a quaternion of bits (in-alarm, fault, overridden, out-of-service) that support provides extra information about the object value.
• Write priority: for the record writing of 'commandable' properties, you can specify the priority 1-16. 1 = top priority, 16 = the lowest priority, 0 = none priority.

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Browsing of address space

When clicking on the "Browse" button in the Address tab of the I/O tag, Bacnet the BACnet Item Browser dialog box opens. In this dialog box, the user may browse the address space of a device and insert its items to the address dialog of the I/O tag.

The items can be filtered through the based on four basic criteria:

• Instance number
• Type
• Object name
• Object description

Note: In case of Type, Object name, and Object description it is not necessary to enter the full text in the filter field. Notation The notation "*FILTERED EXPRESSION*" is supported. The symbol * represents any text before and after the expression.

Note: Using Ctrl+C it is possible to copy the content of Bacnet the BACnet Item Browser into the Windows clipboard. All rows will be copied unless a specific row is selected.

Note: In versions from 20th December 2018 and newer, the recycling of browser dialog has been implemented. If the dialog is closed by the Cancel button or after selecting an object, 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 with the browsed objects is preserved. Clicking on the close icon at the top right corner will cause the dialog to be really closed.

• the element consists of the optional number of context tag, the letter defining the application tag and the value
• the application tags are written as follows (usage with and without context tag):
  • Null: [tag] n, example: " n", " 3n",
  • Boolean: [tag] b [0|1|n|y|N|Y], example: "b0", " 3b1"
  • Unsigned: [tag] u value, example: "u 123", " 10 u123"
  • Signed: [tag] s value, example: "s-123", " 10s 5"
  • Real: [tag] r value, example: "r 1.23", " 10r-3.14"
  • Double: [tag] d value, example: "d 1.23", " 10 d -3.14"
  • Octet string: [tag] O string, every byte of string is written as hex number (byte 1 is 01, byte 26 is 1A), example: "O 1A33f0", " 10 Obb004E"
  • Character string [tag] C 'string', example: "C 'hello world' ", " 10C 'apostrophe '' in the string' "
    The string must enclosed in the apostrophes. If the apostrophe occurs inside the string, it must be double (see the second example). Empty string can be set as follows: " C; "
  • Bit string: [tag] B bits, example: "B 100101", " 23B00101"
  • Enumerated value: [tag] E value, example: "E 123", " 10 E123"
  • Date: [tag] D day.month.year[.day_of_week], example: "D 1.10.2005", " D3.4.2004.5" (Monday=1 .. Sunday=7)
  • Time: [tag] T hour:minute:sec[.ms], example: "T 5:12:33.133", " T10:00:00"
  • Object identifier: [tag] o type:instance or [tag] o objid, (type is a 10-bit number, instance is a 22-bit number, objid is a 32-bit number. The examples show a binary 2-component and a single record -component format of this application tag with type=3 (binary-input) and instance=2
    " o 3:2", " 3o3:2"," 3o 12582914"
• the sequence consists of the single individual elements separated by the blank spaces and/or semicolons, e.g. " 1b0 2u13 ; 3 B 1001;4E14"
• the sequence can contain the nested sequences
• the nested sequence begins with the an optional number of context tag number and an opening bracket character '{'. If any no context tag is not enteredspecified, 0 is used.
• at the end of a nested sequence there is a closing bracket character  '}'
• the an example of nested sequence: "1u2 2{ 1s-1; 2E0 }", two levels of nesting: " { 1{ u23 s34 } 2E56 3r7.89 }"

Note 1: If ASN sequence is a result of the reading of I/O tag from communication is an ASN sequence and the I/O tag is of Txt type, this ASN sequence is written into it (according to the above-mentioned rules) on conditions thatusing the following rules:

• a blank space is before each element is blank space and the element is followed by a semicolon (e.g. " 1E4; 2B111; 3u1;"),
• a blank space is not between the number of context tag and the letter specifying the application tag,
• a blank space is not blank space, between the letter specifying the application tag and the value is not the blank space,
• the a context tag is before every nested sequence (e.g. " 0{ 0o1:2; 1E4; }",
• format of the time is hh:mi:ss.mss, e.g. " T11:01:02.000; 1T12:00:00.000; ",
• format of the date is dd.mm.yyyy, e.g. " D25.01.2005; 3D01.01.2005;".

Note 2: The empty sequence may be recorded written by the a string " ", the string of length 0 (i.e. "") is ignored.

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Note: If the Application tag is not set configured properly (for binary value it is Enum), Desigo station returns an error 'invalid-data-type' when trying attempting to record itwrite:

  error-class ENUM 2 property
  error-code ENUM 9 invalid-data-type	

The Siemens Desigo PXC64-U device requires to set the following parameters for settings of Application tag:

• binary-value, binary-output: Enum
• multi-state-value, multi-state-output: Unsigned
• analog-value, analog-output: Real

Comment on input-output I/O tag: you can configure the I/O tag which is both input and output:
I/O tag of Ao type - Analog output:

• Request type: ReadProperty
• Object type: analog-value(2)
• Instance: 45
• Subscribe/read: Y
• Property type: Simple
• Property identifier: present-value(85)
• Application tag: Real (this is necessary for the record of valuewriting)

When writing the value, the message WriteProperty-Request message is used. As Subscribe/read is tickedchecked, the written value is rereadread after it's written. If I/O tag would be configured with Request type WriteProperty, its behavior would differ only in by an absence of periodic value reading (when starting the KOM process and during its running, the period is set configured on the station, tab in Time parameters tab).

Comment on Siemens Desigo devices: I/O tags has a text name in the Desigo control system. The instance of the I/O tag may be detected found out from the file DOTS00.DAT file in the application  application configuration - it is placed located 24 bytes before the beginning of the name.

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Scheduler in Siemens Desigo devices

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