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7-4 Data Conversion
The word data are regarded as unsigned ( positive ) data in the
Modbus message. However, the actual value of the parameter may
be negative value with decimal point. The high/low scale values for
each parameter are used for the purpose of such conversion.
Let M = Value of Modbus message
A = Actual value of the parameter
SL = Scale low value of the parameter
SH = Scale high value of the parameter
The conversion formulas are as follows:
65535
M =
SH-SL
SH-SL
A =
65535
7-5 Communication Examples :
Example 1: Down load the default values via the programming port
The programming port can perform Modbus communications
regardless of the incorrect setup values of address, baud, parity, stop
bit etc. It is especially useful during the first time configuration for the
controller. The host must be set with 9600 baud rate, 8 data bits, even
parity and 1 stop bit.
The Modbus message frame with hexadecimal values is shown as
follows:
( A
SL)
M + SL
UM0L911C
57
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