Appendix C ______________________________________________________ MODBUS Reference
VAISALA______________________________________________________________________ 207
APPENDIX C
MODBUS REFERENCE
This appendix describes the MODBUS functions and data of the
transmitter.
Function Codes
PTU300 supports all MODBUS conformance class 0 and class 1 function
codes defined in Open MODBUS/TCP Specification, Release 1.0.
Table 40 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 PTU300 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).
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