Owner's manual

Appendix C _________________________________________________________ Modbus Reference
VAISALA _______________________________________________________________________ 177
APPENDIX C
MODBUS REFERENCE
This appendix describes the Modbus functions and data of the
transmitter.
Function Codes
DMT345 and DMT346 support all Modbus conformance class 0 and
class 1 function codes defined in Open Modbus/TCP Specification,
Release 1.0.
Table 46 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 DMT345/346 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).