Xylem Expert 7060_7070_Modbus - Manual (Page 6)

Communication protocol Serie30
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4.8 Function 16: MODBUS Register WRITE
Write a number of subsequent registers on the MODBUS address space starting with StAdd.
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Function is implemented in devices Class.Group-Version = 5.20-10.XX and later
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A register contains 2 bytes (16 bit).
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The number of registers written in one cycle is limited to 2 (0x02) for Class.Group-Version = 5.20-10.XX
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Byte-count of the answer will be an even number (1 register = 2 bytes).
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Addresses above 0xFF00 are virtual command registers that simply execute a task on the slave. Please refer to chapter
“4.9 MODBUS Register Map” for more information.
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Writing float values (0x03XX and 0xFFXX) always requires 2 data registers.
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#Reg in the response declares the number of actually written registers (in case an error occurs, this amount is not the
same as in the request)
Request:
DevAddr 0x10 StAdd H StAdd L # Reg H # Reg L # Bytes Data H Data L
… Data H Data L CRC16 L CRC16 H
Response:
DevAddr 0x10 StAdd H StAdd L # Reg H # Reg L CRC16_L CRC16_H
Error:
DevAddr 0x90 Error CRC16_L CRC16_H
Error codes:
2 Illegal data address:
- Undefined starting-address or wrong number of registers
- Start-address not defined (for writing)
3 Illegal data value:
- The amount of data is out of bound
- Byte-Count is not twice the # Reg.
4 Slave Device Failure:
- Attempted to write into a protected register
- The data written is outside the defined data range