FTS 21216, Руководство по эксплуатации

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700-SDI-RADAR-LX-80-Man Rev 1 08 Oct 2021 32 /49
7.4 MODBUS PROTOCOL (RS-485)
The unit responds to Modbus requests over RS-485 data line. The baud rate is configured through
the PC application, and 1 stop bit, even parity, 8 data bits configuration is used.
Modbus registers that are accessed by Modbus protocol are 16-bit (2-byte) registers. Any number of
registers can be read or written over Modbus.
Modbus is a request-response protocol where a master (such as datalogger) sends out requests,
and slave devices (such as the LX-80 sensor) respond. The request and response format, with
examples is given in Sections 7.4.1 and 7.4.2.
In each request, the master can either ask the slave to retrieve the value of one or more registers, or
the master can set the value of one or more registers. Each register holds one 16-bit value.
7.4.1 MASTER REQUEST FORMAT
Master Request Example
7.4.2 SLAVE (SENSOR) RESPONSE FORMAT
Please note that Modbus register addresses start with 1. The lowest possible address for the
Modbus register is 1. However, in the Modbus request packet the data start address is written as the
address of the first register to read minus one. For example, to retrieve the Modbus register number
5, in the Modbus data packet the address of that register should be written as 4.