EMU - User manual v1.2
Modbus communication
5 Modbus communication
The Decode EMU device supports the Modbus RTU protocol on the RS-485 port. Supported
serial speeds are 1200, 2400, 4800, 9600, 19200, 57600 and 115200 bits per second.
Supported formats are 8 bit and No Parity, Even Parity or Odd Parity.
Device support two modbus functions: 03 - Read holding register and 06 - Preset single
register which may be used only in SETUP mode.
5.1 Supported functions
5.1.1
Function 03 - Read Holding Register
The query consists of 8 bytes. Make sure that only existing registers can be read.
Byte
Field name
Content
1
Device address
x
2
Function
3
3
Register address Hi
x
4
Register address Low
x
5
Register number Hi
x
6
Register number Low
x
7
CRC error check Lo
x
8
CRC error check Hi
x
The response consists of n + 5 bytes, n is from 2 to 34, so the length is from 7 to 39 bytes:
Byte
Field name
Content
1
Device address
x
2
Function
3
3
Bytes number
n
4
Register Hi
x
5
Register Low
x
...
...
...
n+4
CRC error check Lo
x
n+5
CRC error check Hi
x
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