Advanced settings

MAX_OBJ_SUBS_COV_ENTRIES

10 ( 1 - 255 )

The COV subscriptions are managed in TwinCAT BACnet/IP for each object. The default setting is 10 subscriptions per BACnet object. These parameters can be used to specify the maximum number of COV subscriptions per object. For performance reasons it may make sense to reduce the value of this parameter. in order to avoid excessive COV notifications if there are many changes in the system.

MAX_PROPERTY_ARRAYELEMENTS

200 ( 10 - 10000 )

For BACnet properties with array data types in TwinCAT BACnet/IP (data type ends with []), a memory for a pre-defined number of elements is created on startup, so that elements can be added dynamically during operation. By default up to 200 elements can be stored in an array property. If more than 200 elements are configured in an array property in the Settings dialog, additional memory capacity is automatically created during startup in order to accommodate all elements.

LIST_ALLOC_MEM_BYTES

8192 ( 500 - 4294967295 )

For properties with list data type in TwinCAT BACnet/IP (data type ends with list), the memory capacity required per element may vary. On startup a predefined memory is created, so that elements can also be added and modified dynamically for these properties. The default configuration is 8 kbytes. Via this parameter the memory capacity per list property can be defined. As for the array properties, if the property is configured with more memory in the Settings dialog, more memory is created.

MAX_DEVICE_BINDINGS

1000 ( 10 - 10000 )

Each device in the BACnet network (which sends an I-Am packet) is administered in the DeviceBindings table, where all the parameters required for the communication with a device are stored. The size of this table can be specified via this parameter. The table is cleared on each restart and when a scan process is triggered (e.g. in the System Manager).

MAX_OBJECTS

1000 ( 10 - 4294967295 )

BACnet objects for each BACnet client and BACnet server are administered in hash tables. This parameter defines the size of these tables. If a configuration is intended to contain BACnet servers and BACnet clients with more than 1000 objects, this parameter has to be increased. The number of objects refers to the total number of all objects configured under BACnet servers and BACnet clients and must be selected accordingly. When BACnet objects are added in the System Manager or through scanning of BACnet clients this parameter is automatically incremented in steps of 100. To support creation of a large number of dynamic objects at runtime this parameter should be increased manually.

MAX_CLIENTS

255 ( 10 - 10000 )

The clients created in the System Manager are administered in a list. If more than 255 (statically configured in the System Manager) clients are to be used, this parameter must be increased.

MAX_TRENDLOG_ENTRYSIZE

56 ( 56 - 10000 )

For TrendLog objects the memory for the LogBuffer is also created on startup. The parameter BufferSize can be used to specify the number of entries as a BACnet property. The memory size required for an entry depends on the logged property. The minimum size of 56 bytes is adequate for error log entries and for logging simple data types (REAL, Integer ...). If the entry: "Resources:No_space_to_write_property" appears in the LogBuffer, the available memory is not sufficient and the value of this parameter must be increased.

DYN_TRENDLOG_BUFFERSIZE

100 ( 10 - 10000 )

Since the memory for the TrendLog buffer is created when the BACnet object is generated, for dynamically created TrendLog objects the value of the BACnet property BufferSize must be known. This is specified via this parameter.

MAX_MULTISTATE_DYNSTATES

255 ( 2 - 10000 )

For MultiState objects memory must be created for the BACnet property StateText during startup. The maximum possible number of states (NumberOfStates) must be known, since the BACnet property NumberOfStates can be modified during runtime. This parameter defines the maximum value of the property NumberOfStates and therefore the amount of memory to be created during startup.

MAX_RECV_BAC_SEGM_FRAMES

1000 ( 100 - 10000 )

The components of segmented frames have to be held in the buffer, so that they can be recombined to the original message once all components have been received. This parameter has to be set accordingly, depending on the envisaged parallel processing of segmented messages.

MAX_SEND_BAC_SEGM_FRAMES

1000 ( 100 - 10000 )

During sending messages may also have to be segmented. Frames prepared for sending are stored in the table. The size of this table can be set via this parameter.

IO_STARTUP_TIMEOUT

2000 ( 0 - 10000 )

The initialization of a connected fieldbus (K-bus, EtherCAT) may take longer than starting of the BACnet server. This may result in the automatic fieldbus monitoring (Reliability, StatusFlags) setting all IO BACnet objects to an error state, which on the one hand generates trend log entries with set fault bits in the StatusFlags, but may also lead to notifications being sent. The StateMachine of the BACnet server can therefore be delayed by an I/O start time, in order to await successful initialization of the fieldbus during startup.

MAX_PARALLEL_COV_SUBS

250 ( 1 - 255 )

When using client process data in COV mode, slow remote stations may result in communication failures, or COV subscriptions may not be completed successfully. This parameter can be used to set the maximum number of concurrent COV subscription requests per BACnet client.

AVERAGING_MAX_BUFFERSIZE

1000 ( 1 - 10000 )

Sets the size of the internal buffer for averaging. This buffer stores data for the calculation of statistical data (average value etc.). If the calculation is based on more than 1000 samples, this parameter must be increased.

MAX_SENDFRAMES_PERCYCLE

4294967295 ( 1 - 4294967295 )

In order to limit temporary peak loads relating to sent BACnet telegrams, the number of frames to be sent per cycle can be limited. With a cycle time of 50 ms and a value of 1, the maximum number of frames that are sent per second is 20. This mechanism can be used to prevent flooding of the BACnet network in certain cases. However, in general it is better to find the cause for the large number of sent frames and rectify it, e.g. through the use of filters for AnalogInput objects.

PROPOSED_WINDOW_SIZE

16 ( 1 - 127 )

Segmentation is used in BACnet when transferring large amounts of data. The maximum number of open unconfirmed sent messages is "negotiated" when the connection is established. This parameter determines what "window size" (i.e. the number of unconfirmed messages) is suggested by this device. For the CX8091, this value must be reduced to 4, because otherwise file access will not work due to limited network storage.

FREERUN_CYCLETIME_MODULO

10 ( 1 - 100 )

In Freerun mode, the internal state machines of the BACnet objects are called with a cycle time of 2 ms. For large BACnet configurations this can lead to system overload. This parameter specifies after how many cycles BACnet objects are called. In the default case (10), the BACnet objects are therefore processed only every 20 ms.

ARCHIVE_BUFFER_SIZE

65535 ( 65535 - 16777216 )

A buffer is used for persistent data that have to be stored. This buffer should be at least as large as the largest property in the system. Typically, it is the property LogBuffer of a TrendLog object. With a size of 40 bytes per entry (normal value, no error), the default value of 65535 for this parameter is exceeded from 1638 entries. In this case, this parameter should be increased. With a LogBuffer of 3000 entries, the value should therefore be set to 120,000 bytes (40*3000)