Isolated RS485 serial communication to 4-20mA0-10V analog output DA module PLC expansion

1. Module parameter configuration
The module can configure the module address, baud rate, output value and parameter compensation parameters through the Modbus RTU protocol, function number 06, and query the corresponding configuration information through function number 03. Since the parameters are saved in the internal E2PROM memory, its write life is 10000 times, do not write frequently.
2. Module address configuration (default 01)
Module address range: 1-245
Register address Function number Function description Read/write
0x0000 06 Write module parameters: address write

For example:
The host sends: 01 06 00 00 00 02 08 0B (hexadecimal)
01 module address, 06 function number, 00 00 is the holding register address to be written, 00 02 is the write data, a 16-bit data, the lower 8 bits of data are valid, 00 02 means change the module address to address 2, 08 0B It is the CRC check code.
Module return data: 01 06 00 00 00 82 (hexadecimal)
After receiving the returned data, the parameters take effect immediately.
Note: When the module address is forgotten, you can send a broadcast (address 00) to configure, but you must ensure that there is only one module on the bus and the broadcast command does not return. An example is as follows:
The host sends: 00 06 00 00 00 01 49 DB (hexadecimal) to configure the module address as 01 through the broadcast.
3. Module baud rate configuration (default 02)
Register address Function number Function description Read/write
0x0001 06 Write module parameters: Baud rate write

Configurable baud rate range: 2400, 4800, 9600, 19200, 38400, 57600
00:2400 01:4800 02:9600 (default) 03:19200 04:38400 05:57600
Invalid input: 9600
For example:
The host sends: 01 06 00 01 00 02 59 CB (hexadecimal)
01 module address, 06 function number, 00 01 is the holding register address to be written, 00 02 is the write data, the lower 8 bits of data are valid, 00 02 means the module baud rate is configured to 9600, 59 CB is the CRC check code.
The module returns data: 01 06 00 01 00 C2 (hexadecimal) receives the returned data, and the parameters take effect immediately.

4. Module output configuration (E2PROM is not saved, the default output is 0 after power-on)
Register address Function number Function description Read/write
0x1000 06 Write module output value Read and write

Configuration output range: 0-25000
For example:
Host sending: 01 06 10 00 27 10 97 36 (hexadecimal)
01 module address, 06 function number, 10 00 is the holding register address to be written, 27 10 is the write data (corresponding to 10000), 97 36 is the CRC check code.
The module returns data: 01 06 00 01 00 C2 (hexadecimal) receives the returned data, and the parameters take effect immediately.