9.3.5 SLC-5/05 Example: Reading and Writing
Often times, applications may need to both read data from and write data to the inverter. To accomplish
this task, multiple MSG instructions will need to be implemented in the PLC program. The configuration
and execution for implementing multiple MSG instructions is in general identical to that required for
implementing just one MSG instruction. Each MSG instruction will require its own message control file.
Figure 86 shows an example of two MSG instructions, one for reading and one for writing. It is evident
from this logic that N20 and N21 are the two independent message control files created for these
instructions. Note that the “Read/Write” field of each of the MSG instructions is set according to their
function.
Figure 86: Reading and Writing via MSG Instructions
Figure 87 shows the configuration details of the “write” MSG instruction. Note that this instruction will
only be writing to one inverter register: namely, register 1798 (function code S05 / frequency command).
The source Data Table Address in this case is N18:30.
Figure 87: MSG Configuration for Writing
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