CIMPLICITY supports reconfiguration of point properties while the project is running. The point properties that directly impact the behavior of the Modbus RTU Slave Interface include the following:
Access rights
Data type
Array size
The Modbus RTU Slave Interface monitors the project database for changes in point properties. Once notified, point property changes are applied immediately.
Example
Changing the access rights for a point from read-write to read-only will cause Modbus write requests (that specify the corresponding data address) to fail.
In particular, changes to the array size of a point may have unexpected results. At startup, the Modbus RTU Slave Interface determines the array size for every mapped point. By definition, a scalar point has an array size of 1. In combination with other tests, the Modbus RTU Slave Interface uses the array size to ensure that every array element is mapped to a unique Modbus data address. The array size determined at startup becomes the maximum size allowed. Thus, while the array size may be reduced, the Modbus RTU Slave Interface ignores increases.
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Expected Modbus RTU Slave runtime behavior. |
