Appendix B _________________________________________________________ Modbus Reference
VAISALA _______________________________________________________________________ 103
APPENDIX B
MODBUS REFERENCE
This appendix describes the Modbus protocol implementation of the
HMW90 series digital transmitters.
NOTE
If a register is not relevant for the transmitter model, it does not exist
("illegal data address" code is returned).
Function Codes
Conformance class 0 function codes are enough to access the
measurement data and configuration settings of HMW90. In addition,
some class 1 commands are also supported, giving better compatibility.
Device identification data can be read out only with the function code
dedicated for that purpose (43 / 14).
Table 39
Supported Function Codes
Function Code
Name
Notes
03 (0x03)
Read Holding Registers
Class 0
04 (0x04)
Read Input Register
Class 1
06 (0x06)
Write Single Register
Class 1
16 (0x10)
Write Multiple Registers
Class 0
43 / 14 (0x2B / 0x0E)
Read Device Identification
