Datakom DKM-409 PRO AT, Руководство пользователя

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DKM-409 Pro AT User Manual Rev_02 Firmware V-2.5
K91D01-EN - 52 -
The unit offers the possibility of MODBUS communication through below carrier:
-RS485 serial port, with adjustable baud rate between 2400 and 115200 bauds
The MODBUS properties of the unit are:
-Data transfer mode: RTU
-Serial data: selectable baud rate, 8 bit data, no parity, 1 bit stop
-Supported functions:
-Function 3 (Read multiple registers)
-Function 6 (Write single register)
-Function 16 (Write multiple registers)
Each register consists of 2 bytes (16 bits). A larger data structure will contain multiple registers.
The Modbus communications requires a slave address to be assigned to each device in the Modbus
network. This address ranges between 1 and 240 and allows the addressing of different slave devices in the
same network.
Modbus Slave Address:
may be set between 1 and 240
RS-485 Enable: must be set to 1 (or checkbox enabled)
RS-485 Baud Rate: selectable between 2400 and 115200 bauds. All devices in the same network must use
the same Baud Rate.
Selecting a higher baud rate will allow faster communication, but will reduce the communication distance.
Selecting a lower baud rate will increase the communication distance, but will cause slower response times.
Typically 9600 bauds will allow 1200m distance with special balanced 120 ohms cable.
16bit variables: These variables are stored in a single register. Bit_0 denotes the LSB and bit 15 denotes
the MSB.
32 bit variables: These variables are stored in 2 consecutive registers. The high order 16 bits are in the first
register and the low order 16 bits are in the second register
Bit arrays: Arrays larger than 16 bits are stored in multiple registers. The LSB of the first register is bit_0.
The MSB of the first register is bit_15. The LSB of the second register is bit_16. The MSB of the second
register is bit_31, and so on.
Data read can be achieved by using function 03 (read multiple register). MODBUS master device sends
query. Respond can be either requested data or failure message including reading fail. 123 Registers can be
read by single message. If a single message includes query for more than 123 registers, first 123 registers
will be returned. Message structure can be seen below.
21. MODBUS COMMUNICATIONS
Each device in the same RS-485 serial network must be
assigned a different slave address. Otherwise the Modbus
communications will not be performed.
21.1. PARAMETERS REQUIRED FOR RS-485 MODBUS OPERATION
21.2. DATA FORMATS
21.3. DATA READ