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Driver Manual
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Page 20
4.4.8 Map Descriptor: Example 3 – Writing multiple points using one message.
Map_Descriptor_Name, Data_Array_Name , Data_Array_Offset, Function, node_name, Address, Length, DA_Field , DA_Assoc, Scan_Interval
Write_MapDesc_1, DA_ SETPOINTS, 0 , wrbc, unit1 , 0 1 , nom_h_setpt , 2 , 120.0s
Write_MapDesc_1, DA_SETPOINTS , 1 , passive, unit1 , 0 1 , t_setpt , 2
A 'Write' and a passive to the same node.
This write will update two fields, the
nom_h_setpt and the t_setpt.
The write MapDesc. Must precede the
passive.
This method is only appropriate if you plan
to continuosly write to the devices. If you
intend to write on change using the wrbx
function then use multiple map descriptors
that are not associated and give each one a
wrbx.
Associate the passive map descriptor to the
active (wrbc) map descriptor. In this way the
driver will use only one message to write to
the device. The message will be built using
both map descriptors. This method reduces
the communication load.
The association is made using the DA_Assoc
parameter. Use unique positive integers.
Omitting the DA_Assoc parameter when
using ‘passive’ map descriptors will produce
ambiguous results.