Xylem Expert 7060_7070_Modbus - Manual (Page 2)

Communication protocol Serie30
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1 Introduction ............................................................................................................................................................................ 3
2 Bit transfer layer (physical layer) ......................................................................................................................................... 3
2.1 Introduction ........................................................................................................................................................................... 3
2.2 Characteristic ........................................................................................................................................................................ 3
2.3 RS485 half-duplex details ..................................................................................................................................................... 4
3 Data-link layer......................................................................................................................................................................... 5
3.1 Transmission format for the serial interface.......................................................................................................................... 5
3.2 Format of a message ............................................................................................................................................................ 6
3.3 Principle of message interchange......................................................................................................................................... 7
4 MODBUS communication...................................................................................................................................................... 9
4.1 MODBUS Communication Basics......................................................................................................................................... 9
4.2 Using MODBUS with KELLER products ............................................................................................................................... 9
4.3 Description of MODBUS functions...................................................................................................................................... 10
4.4 Modbus Communication Examples..................................................................................................................................... 10
4.5 Function 3: MODBUS Register Read.................................................................................................................................. 10
4.6 Function 6: MODBUS Single Register Write....................................................................................................................... 11
4.7 Function 8: MODBUS Echo Test ........................................................................................................................................ 11
4.8 Function 16: MODBUS Register WRITE............................................................................................................................. 12
4.9 MODBUS Register Map...................................................................................................................................................... 13
4.10 Device Operation Command List ...................................................................................................................................... 16
5 Description of Keller bus functions ................................................................................................................................... 17
5.1 Example: read pressure value with exception handling...................................................................................................... 17
5.2 Function 30: Read coefficient.............................................................................................................................................. 18
5.3 Function 31: Write coefficient.............................................................................................................................................. 20
5.4 Function 32: Read configuration ......................................................................................................................................... 21
5.5 Function 33: Write configuration ......................................................................................................................................... 21
5.6 Function 48 : Initialise and release...................................................................................................................................... 23
5.7 Function 66 : Write and read new device address............................................................................................................. 24
5.8 Function 69 : Read serial number...................................................................................................................................... 24
5.9 Function 73 : Read value of a channel (floating point)....................................................................................................... 25
5.10 Function 74 : Read value of a channel (integer) ............................................................................................................... 26
5.11 Function 95 : Commands for setting the zero point .......................................................................................................... 27
5.12 Function 100 : Read configuration .................................................................................................................................... 28
5.13 Function 101 : Write configuration .................................................................................................................................... 28
6 Appendix............................................................................................................................................................................... 30
6.1 Interface converter .............................................................................................................................................................. 30
6.2 floating-point format IEEE754 ............................................................................................................................................. 30
6.3 Error handling and recognition............................................................................................................................................ 31
6.4 Calculation of the CRC16 checksum .................................................................................................................................. 33
6.5 Description of the software driver (DLL).............................................................................................................................. 34
6.6 Changes.............................................................................................................................................................................. 37
6.7 Software versions................................................................................................................................................................ 37
6.8 Support................................................................................................................................................................................ 37
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