6.3.6 Mapping application parameters to Modbus registers
Applications parameters support either extended or basic read/write mechanism.
Extended read/write
The following extended mapping examples illustrate:
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BA analog output object represented on Modbus by 4 holding registers
●
BA analog input object represented on Modbus by 4 input registers
●
Data item size is 4 in both cases
Example of an analog input object (extended read):
Input register address
Data item structure
X
X+1
Present value
X+2
Status flags
Voidfield(=0:0)
X+3
Reliability
Example of an analog output or value object (extended read/write):
Holding register address
Data item structure
X
X+1
Present value
X+2
Status Flags
Cmd(=Ready)
Priority
X+3
Reliability
Register
address
b15 b14 b13 b12 b11 b10 b9
b8
b7
b6
b5
b4
b3
b2
b1
b0
x
Present value
x+1
x+2
r(0)
r(0)
r(0)
r(0)
Status flags
Cmd
Priority
x+3
Reliability
Data item structure for 32bit data and Mapping=Extended
Engineering of communicative devices
Modbus slave
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