ProSoft Technology CompactLogix MVI69E-MBS User Manual page 128

MVI69E-MBS ♦ CompactLogix™ Platform
Modbus Serial Enhanced Communication Module
The next few pages show three specific examples:
Example #1: Master is issuing Modbus command with FC 16 (with Float Flag: Yes) to transfer Float
data to slave.
(Float specific module parameters)
Float Flag: "Y" tells the master to consider the data values that need to be sent to the
slave as floating point data where each data value is composed of 2 words (4 bytes or
32 bits).
Float Start - Tells the master that if this address number is <= the address number in
Addr in Dev parameter to double the byte count quantity to be included in the Command
FC6 or FC16 to be issued to the slave. Otherwise the master ignores the Float Flag: Y
and treat data as composed of 1 word, 2 bytes.
(Modbus Command parameters)
DB Addr - Tells the master where in its data memory is the beginning of data to obtain
and write out to the slave device.
Reg Count - Tells the master how many data points to send to the slave. Two counts
mean two floating points with Float Flag: Y and the Addr in Dev greater than or equal to
the Float Start Parameter.
Swap Code - Tells the master how to orient the Byte and Word structure of the data
value. This is device dependent. Check Command Entry formats Section.
Func Code - Tells the master to write the float values to the slave. FC16.
Addr in Dev - Tells the master where in the slave's database to locate the data.
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Reference
User Manual
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