70
line-CVM-D32
Instruction Manual
7�2�- MODBUS PROTOCOL
The
MODBUS
protocol is a standard communications protocol in industry enabling networking of mul-
tiple devices, involving a master and multiple slaves. It enables individual master-slave dialogue and
also allows commands in broadcast format.
The
MODBUS
protocol used by the
line-CVM-D32
device implements the RTU (Remote Terminal Unit)
mode.
In RTU mode, message start and end are detected with a 3.5 minimum character silence and the 16-bit
CRC error detection method is used.
The
MODBUS
functions implemented in the device are:
Function 0x04
and
0x03
: Register readout.
Function 0x02
: Input status readout.
Function 0x10
: Writing multiple registers.
Function 0x01
: Relay status readout
Function 0x05
: Writing a relay status.
7�2�1�- MODBUS QUERY EXAMPLE
Question:
Instantaneous value of L1 phase voltage.
Address
Function
Initial
register
No� of
registers
CRC
0A
04
0000
0002
xxxx
Address: 0A
, Peripheral number: 10 en decimal.
Function: 04
, Read function.
Initial register: 0000
, desired register to start readout.
Nº of registers: 0002
, number of registers to read.
CRC: xxxx
, CRC character.
Response:
Address
Function
No� of bytes Register no� 1 Register no� 2
CRC
0A
04
04
0000
084D
xxxx
Address: 0A
, Number of peripheral responding: 10 in decimal.
Function: 04
, Read function.
No� of bytes: 04
, No. of bytes received.
Register: 0000084D
L1 phase voltage value: VL1 x 10 : 212.5V
CRC: xxxx
, CRC character.