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4.4.6.Map Descriptor: Example 3 – Writing multiple points using one message.
Additional information is provided in Appendix B
// Client Side Map Descriptors
Map Descriptors |
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Map_Descriptor_Name, | Data_Array_Name, | Data_Array_Offset, | Function, | Node_name, | Address, | Length, | DA_Field, | DA_Assoc, | Scan_Interval |
Write_Map Descriptor_1, | DA_SETPOINTS, | 0, | WRBC, | Unit1, | 0, | 1, | nom_h_setpt, | 2, | 120s |
Write_Map Descriptor_1, | DA_SETPOINTS, | 1, | passive, | Unit1, | 0, | 1, | t_setpt, | 2, |
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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 Map Descriptor. must precede the passive. For a Dart, use wrbx instead of wrbc.
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.
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