Parameter Description
Function Type
Function type - depends on the type of the data (see manual of the Modbus
device).
1: Read Coils
2: Read Inputs
3: Read Holding Registers
4: Read Input Registers
Currently function codes 1..4 are supported.
Slave Number Address/Slave number of the Modbus device.
Start Address Start address (offset) of the data.
Quantity Quantity of data to be read.
VariableType
You can choose the following variable types of the Modbus data to be read:
1: char
2: unsigned char
3: short
4: unsigned short
5: long
6: unsigned long
7: float
8: double
9: ASCII-Text
Real Type
Real type - determines, if the registers of real values have to be processed in
reversed order
0: Normal order
1: Reversed order
2: Byte swap order
3: Word swap order
Real types 2 and 3 are available from V03.04.02.01.
Response Address
Offset
Offset of the data to return in register units.
Response Quantity
Quantity of the returned data. Only for string data a value greater than 1 is
supported.
Addressing:
The information is stored in the Modbus Slave device in 4 different tables. 2 tables store on/off
discrete values (coils) and two store numerical values (registers). Each coil is 1 bit long and
assigned a data address between 0 and 65535. Each register has the size of 1 word(16 bits/ 2
bytes) and has a data address between 0 and 65535.
Coil/ Register numbers Data addresses Function type Table name
1-9999 0 to 65535 1 Read Coils
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