Honeywell RAEGuard 3 - Modbus Protocol

RAEGuard 3 User Manual
81
Appendix A - Modbus
®
Protocol:
RAEGuard 3 detectors support RS485 data transmission and communicate
as MODBUS RTU. The detector provides 4-byte register data.
Note: The communication only transmits the tested concentration value of
the gas.
For example: 34 hex = 52 decimal
RAEGuard 3 detector supports RS-485 ModBus communication function.
The following are the communication protocols that support this
communication.
 Communication settings
Communication mode: RTU
Baud rate: 4800，9600，19200，38400，57600
 Information structure / communication steps
RAEGuard 3 only supports the 0x03 (read-only register) function code, i.e.
The detector only supports reading values.
0x03: Read-only register
Request information:
Device
Address
Function
Code
Register
Address
High Byte
Register
Address
Low Byte
Quantity of
Registers
High Byte
Quantity of
Registers
Low Byte
CRC
Low
Byte
CRC
High
Byte
Client ID
03
00
08
00
02
CRC
CRC
Response information:
Device
Address
Function
Code
Byte
Count
Register Value
CRC
Low
Byte
CRC
High
Byte
Client ID
03
04
Reading
Highest
Byte
Reading
Higher
Byte
Reading
High
Byte
Reading
Low
Byte
CRC
CRC
Note: The data sent by the detector is 4 bytes long.
For example:
Request: 01 03 00 08 00 02 45 C9
Response: 01 03 04 00 00 00 D1 3A 6F
Note: The maximum transmission distance of standard 1.5 mm
2
communication cable is less than 1 km.