ICC
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8.2.9 ControlLogix Explicit Messaging Example: Read a Single Register
The configuration and execution for reading a single register is in general identical to that required for
reading a block of registers as detailed in section 8.2.8. The only difference is in the configuration of the
MSG instruction. Figure 113 shows an example MSG instruction’s Configuration tab, which will read a
single tag (rd_reg_2063 / function code M14, the inverter’s operation status register) and place it in the
first element (offset 0) of data_array.
Figure 113: Read the Inverter's Operation Status Register
8.2.10 ControlLogix Explicit Messaging Example: Multiple MSG Instructions
At times, reading from different groups of registers may be necessary. For example, a specific
application may require access to some registers in both the Monitor Data 1 and Monitor Data 2 function
code groups. 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
controller tag. In the case of read MSG instructions, more than one instruction may use the same
Destination Element tag, but the storage locations must not overlap. Figure 114 shows an example of
two MSG instructions, each accessing different read tags. It is evident from this logic that
“rd_connection” and “rd_connection2” are the two independent message controller tags created for
these instructions.
Figure 114: Reading Via Multiple MSG Instructions
