ProSoft Technology PS-QS-1x10-0781 - Manual (Page 18)

FieldServer Configuration Manual Page 18 of 90
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4.3 Active Map Descriptor Functions
A Responsible Map Descriptor is a Map Descriptor that inherently monitors the quality of the data that it is
mapping and can be recognized by the “Function” parameter field. The following are all Responsible Map
Descriptors.
4.3.1 Read Block Continuous (Rdbc)
The Rdbc function will read a block of data of length specified by the “length” parameter, and transfer that data to
the Data Array specified. Reads are performed continuously at an interval specified by the “Scan_Interval”
parameter.
The Rdbc function also has the ability to perform what is known as “write throughs”. If the driver allows writing to
the point related to the Map Descriptor where Rdbc is specified, then the Rdbc function will write the data in the
Data Array back to the point when an update in the associated Data Array is detected. This makes Rdbc the ideal
function for read/write points.
4.3.2 Active Read Continuous with Sequencing (A rcs).
This function will perform the same operation as an Rdbc (Arc) function, but will sequence through the range of
addresses starting at "Address" and wrapping at "Address + Length". A length of 1 will be used for every one of the
Addresses that gets polled. The following drivers currently support the ARCS function.

Modbus_RTU

Lutron_Machine

BACnet MS/TP, BACnet Arcnet, BACnet

Metasys N2
4.3.3 Write Block on Change (Wrbx)
The Wrbx function will write data from the Data Array to the remote device. The write is triggered by a change in
the associated Data Array. If the associated Data Array is updated a write will occur, even if the value/s within the
Data Array have not changed. The “Scan_Interval” parameter is not required for this function as writes are event
driven and not continuous.
4.3.4 Write Block Continuous (Wrbc)
This is similar to the Wrbx function, except that the writes occur at a regular interval rather than on an event
driven basis. The frequency of the writes is determined by the “Scan_Interval” parameter.