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8 Modbus Commands
Only the Modbus commands shown in the table 8-1 are supported by the
I-7242D. The structure of the query and response frames for each of these
commands is then described in the following section.
Function Code
0x01
0x02
0x03
0x04
0x0F
0x10
In the table 8-2, each byte of the query and response frames of the
Modbus command are described with the excepted of the field shown opposite.
These are always present in the queries and responses of all Modbus
command.
Table 8-2 Frames of a Modbus command
Device address
Function code
... Other fields ...
CRC (LSB)
CRC (MSB)
It's a better idea to get hold of a standard Modbus document, such as the
guide entitled Modicon Modbus Protocol Reference Guide, so that you can see
the correspondence between the elements displayed in Utility and the content
of the corresponding Modbus frames
I-7242D DeviceNet/Modbus RTU Gateway User's Manual, July 2006, Version 1.1
Table 8-1 Support commands of I-7242D
Preset Multiple Registers
Value
Modbus device address: 1 to 247.)
Value can not be changed (code of the
Modbus command)
...
Specific
commands ...
Cyclic Redundancy Check, containing
16-bit binary value
Modbus Command
Read Coil Status
Read Input Status
Read Holding Registers
Read Input Registers
Force Multiple Coils
cannot
be
changed
features
I-7242D user manual
(Valid
of
Modbus
106/124
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