Lightstar KDX-300, Инструкция по эксплуатации

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6.1 MODBUS Communication specification
Interface
Baud Rate
Data Format
Transmit Method
Error Checking
RS-485 (2Wire) (A+,B-,Com)
9600,14400,19200
1 StartBit,8 DataBits, 1 StopBit (NoneParity)
Half Duplex Asychronous
CRC (Cyclical Redundancy Check)
Tem No Function code Start address HI Start address LO
Length HI Length LO CRC LO CRC HI
0xFF 0x04 0xXX 0xXX 0xXX 0xXX 0xXX 0xXX
CRC HI
0xXX
6.3 Function Code
Request
Item No.
Function code
Byte Count Data HI Data LO ... CRC LO
0xFF 0x04 0xXX 0xXX 0xXX ... 0xXX
Response
→ Read input register structure : Function code No.4
Chapter_6. Communication
Page.22
6.2 Modbus RTU Protocol
Slave Address
n x 8 bits 16 bits 8 bits 8 bits
1) Slave Address: Device address, which is the number between 0~255.
2) Function Code: Function(command) code of Modbus Protocol; it can designate reading and writing of data.
(This device uses function code04 ‘Read Input Register’, and function code05 ‘Force Single Coil’.)
4) CRC Code: Error checking in the communication data.
* Example of Communication (hexadecimal Code)
READ Code : FF. 04. 00. 00. 00. 39. A4. 02 (Read 57 Word)
WRITE Code : FF. 05. 00. 29. FF. 00. 48. 2C (Write DO1 ON)
3) Data: Byte group including the beginning address according to requests/responses, request points,
and input data; composed of high, low 2 Byte per 1 data point.
Function Code Data CRC code