Configuration as a Modbus Slave MVI56E-MCM ♦ ControlLogix Platform
User Manual Modbus Communication Module
Page 66 of 209 ProSoft Technology, Inc.
The length of the copy statement is determined by the Dest file size. To copy 10
floats from the MCM_Write_Floats array to the MCM.DATA.WRITEDATA array,
the length of the COP statement must be set to a value of 20.
To copy data from the MVI56E-MCM module to a floating-point tag within the
ControlLogix processor
1 Configure a tag within the ControlLogix processor as shown.
2 Then configure the COP statement to move data from the
MCM.DATA.READDATA array, and over to the new tag MCM_READ_FLOATS
tag as shown here.
Once again, the COP statement will take as many of the Source elements
required to fill the Dest tag for the length specified. Therefore, the COP statement
will take MCM.DATA.READDATA[0] TO [19] to fill the MCM_READ_FLOATS[0] TO
[9].
3.4.1 Enron/Daniel Float Configuration
Sometimes it is necessary for the module to emulate Enron or Daniel floating-
point addressing.
Copying the data to the MCM.DATA.WRITEDATA array and from the
MCM.DATA.READDATA array is the same as described in the section above. The
main difference is the addressing of the module.
For example, an Enron Float device is required to access address 47001 for
floating-point data, and each Modbus register would emulate a single float value
(does not require 2 Modbus addresses for 1 float value).
A Master device requiring this type of addressing, would require that for every
count of 1, the MVI56E-MCM module responds to the request message with 4
bytes (one 32-bit REAL) value.
To emulate this addressing, the module has the parameters
MCM.CONFIG.PORTX.FLOATFLAG, FLOATSTART, and FLOATOFFSET.
Tells the module to use the FloatStart and FloatOffset parameters
listed below
Determines what starting address on the Modbus network to treat
as floating-point data. A value of 7000 will signal the module that
address 47001 on the Modbus network is the starting location for
Modbus floating-point data. Every address will occupy 2 registers
within the modules database
Determines the address within the module to which to associate
the data from the FloatStart section.
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