Configuring the MVI56E-MCMR Module MVI56E-MCMR ♦ ControlLogix Platform
User Manual Modbus Communication Module with Reduced Data Block
Page 72 of 223 ProSoft Technology, Inc.
Along with the Function Code 3, MB Address in Device 256 will read Modbus
address 40257 of the slave device. The above command will read 40257 and
40258 of the Modbus Slave #1 and place that data in
MCMR.DATA.READDATA[0] and [1].
Within the controller tags section of the ControlLogix processor, it is necessary to
configure a tag with the data type of "REAL" as shown in the following illustration.
Copy data from the MCMR.DATA.READDATA[0] and [1] into the tag
ENERGY_CONSUMPTION that has a data type of REAL. Use a COP statement
within the ladder logic. Here is an example.
Because the tag MCMR.DATA.READDATA[0] should only be used within the
above command, an unconditional COP statement can be used.
Notice the length of the COP statement is a value of 1. Within a Rockwell
Automation processor, a COP statement will copy the required amount of
"Source" values to fill the "Dest" tag for the Length specified.
Therefore, the above statement will copy ReadData[0] and [1] to fill the 32 bits
required for the tag "Energy_Consumption".
Note: Do not use a MOV statement. A MOV will convert the data from the Source register to the
destination register data type. This would create a data casting statement and will result in the loss
or corruption of the original data.
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