User guide

www.rletech.com 67 970.484.6510
A Modbus Communications
A.3. RTU Framing
The example below shows a typical Query/Response from an Wireless Gateway.
Slave address 2 responds to Function Code 4 with six bytes of hexadecimal data and ends with
CRC16 checksum.
Register Values:
40001 = 0000 (hex)
40002 = 0000 (hex)
40003 = 0001 (hex)
Register Name Description Units Range
40001 Id Sensor Identification number uint16 0-65535
40002 Out Of Service Shows when the sensor is in
maintenance mode or offline
uint16 0-65535
40003 Serial # Wireless sensor serial number uint16x4 0-65535
40007 Raw Data #1 First data value displayed by
sensor
Unsigned 32 bit
integer
0-4294967295
40009 Raw Data #2 Second data value displayed
by sensor
Unsigned 32 bit
integer
0-4294967295
40011 Raw Data #3 Third data value displayed by
sensor
Unsigned 32 bit
integer
0-4294967295
40013 Converted Data #1 First data value converted by
the Wireless Gateway
Unsigned 32 bit
integer
0-4294967295
40015 Converted Data #2 Second data value converted
by the Wireless Gateway
Unsigned 32 bit
integer
0-4294967295
40017 Converted Data #3 Third data value converted by
the Wireless Gateway
Unsigned 32 bit
integer
0-4294967295
40019 Age Time since last transmission
received
Unsigned 32 bit
integer
0-4294967295
48001 Offline Delay Time till the sensor reads
offline
uint16 0-65535
Table A.3 Output Registers
Slave
Address
Function
Code
Count Bytes
of Data
Register
Data
Msb Lsb
Register
Data
Msb Lsb
Register
Data
Msb Lsb
CRC 16
“Lsb”
CRC 16
“Msb”
02 04 06 00 00 00 00 00 01 B5 A3
Table A.4 Response Sample