General Measure GMT-H1, Operating Instruction

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Chapter 8 MODBUS communication
8.1 the Modbus protocol
Gmt-h1 Supports one RS485 serial port and one network
port.
Supports modbus-RTU (serial port), Modbus-TCP/IP(network port)
communication mode and automatic reporting mode.
8.2 MODBUS Function Code and Exception Code

Function codes supported by the instrument:
Functi
on
code
The name
of the
instructions
03 Read the
register
A maximum of 125 registers are read at a
time
06 Write a
single
register
16
Write
multiple
registers
This command only supports writing dual
registers, and the address must be aligned
when writing. It is not allowed to write only
part of the dual registers, and it is allowed
to read only part of the dual registers.
01 Read the
coil
Note that this length is in bits
05 Write the
coil
Note: this meter only supports the above MODBUS function codes,
the meter will not respond to other function codes.

MODBUS exception code response
code The name of
the
meaning
02 Invalid data For this meter, the error code indicates