Siemens SIMATIC S7 CP340 Programming Manual page 44

5 MODBUS RTU Protocol communication
Modbus initial
address and length
Fig. 76: Modscan32 operation interface
4. The 10 address data of the data display area correspond to the numeric values
(1-10 for DBW0 - DBW10 respectively)of the first 10 words of DB1 in CPU, as
shown in the Fig. below.
Fig. 77: DB1 data monitor
5. It is only necessary to change the accessed data type in order to read other
data, which is not introduced here.
6. For display of floating point number, it shall be explained that the high 16 bits
and low 16 bits of the floating point number in PLC are opposite to those displayed
in Modscan32, or in other words, the high 16 bits of the floating point number in
PLC correspond to the low 16 bits of the floating point number displayed in
Modscan32, and the low 16 bits of the floating point number in PLC correspond to
the high 16 bits of the floating point number displayed in Modscan32, which may
be handled in the program, as shown in the Fig. below:
CP340/CP341/CP440/CP441 Communication and Programming
Entry-ID: 88867653, V1.0,
Set data display method
Type of data accessed by
Modbus
02/2014
Modbus slave
address
Data display area
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