Appendix A.10. Specifying Readpropertymultiple And Writepropertymultiple Transactions Using Linked Map Descriptors - FieldServer FS-8704-06 Driver Manual

FS-8704-06 BACnet IP Driver Manual
Appendix A.10. Specifying ReadPropertyMultiple and WritePropertyMultiple Transactions using Linked
Map Descriptors
The ReadPropertyMultiple (RPM) and WritePropertyMultiple (WPM) BACnet services allow many objects and
attributes to be read and written in a single transaction. Since FieldServer Map Descriptors can only refer to a
single object type and address range, a RPM or WPM transaction can be constructed by linking multiple Map
Descriptors. This is done using the following components:

an active read or write Map Descriptor that defines the behavior of the RPM or WPM transaction via:

Function, e.g. Rdbc, Arcs, Wrbc, Wrbx

Scan_interval

Timeout

Length

any number of Linked Map Descriptors specifying additional objects and data array locations to be included in
the transaction. Each Linked Map Descriptor is specified with the following settings:

Linked_Map_Descriptor - this is a reference by name to the active Map Descriptor described above,
which controls the transaction

Function - Passive_Client

Length
The number of Linked Map Descriptors is limited by the maximum message length allowed for the BACnet driver in
question. When too many Map Descriptors have been linked a SEGMENTATION_NOT_SUPPORTED error message
will be generated on the first poll attempt. This message will recommend splitting the RPM or WPM transaction
into multiple transactions, e.g.
DRV->BACnet : Linked Map Desc. "CMD_WPM" is too long.
Message Segmentation not supported.
Please split the transaction into multiple Linked Map Descriptors.
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