Appendix B ______________________________________________________ MODBUS Reference
VAISALA ______________________________________________________________________ 185
APPENDIX B
MODBUS REFERENCE
This appendix describes the MODBUS functions and data of the
transmitter.
Function Codes
DMT340 supports all MODBUS conformance class 0 and class 1
function codes defined in Open MODBUS/TCP Specification,
Release 1.0.
Table 34
Supported Function Codes
Function Code
Name
Notes
01 (0x01)
Read Coils
Class 1
02 (0x02)
Read Discrete Inputs
Class 1
03 (0x03)
Read Holding Registers
Class 0
04 (0x04)
Read Input Registers
Class 1
05 (0x05)
Write Single Coil
Class 1
06 (0x06)
Write Single Register
Class 1
07 (0x07)
Read Exception Status
Class 1
08 (0x08)
Diagnostics
15 (0x0F)
Write Multiple Coils
Class 2
16 (0x10)
Write Multiple Registers
Class 0
22 (0x16)
Mask Write Register
Class 2
23 (0x17)
Read/Write Multiple Registers
Class 2
43 / 14 (0x2B / 0x0E)
Read Device Identification
Class 0 function codes are enough to access all measurement data and
configuration settings of the DMT340 transmitter. In addition, all class 1
and some class 2 commands are also supported giving better
compatibility and allowing more efficient communication when needed.
MODBUS diagnostic and device identification data can be read out only
with the function codes dedicated for those purposes (08 and 43 / 14).
