Appendix A - Modbus ® Protocol - Honeywell RAEGuard 3 User Manual

Appendix A - Modbus
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 Function
Address Code
Client ID 03
Response information:
Device Function
Address Code
Client ID 03
Note: The data sent by the detector is 4 bytes long.
For example:
Request:
Response:
Note: The maximum transmission distance of standard 1.5 mm
communication cable is less than 1 km.
®
Register Register
Address Address
High Byte Low Byte
00 08
Byte
Count
Reading
04 Highest
Byte
01 03 00
01 03 04
81
RAEGuard 3 User Manual
Protocol:
Quantity of
Registers
High Byte
00
Register Value
Reading Reading
Higher High
Byte Byte
08 00 02 45
00 00 00 D1
Quantity of CRC
Registers Low
Low Byte Byte
02 CRC
CRC
Low
Byte
Reading
Low CRC
Byte
C9
3A 6F
2
CRC
High
Byte
CRC
CRC
High
Byte
CRC