User guide

Communication protocol Serie30 Page 12/37
4.8 Function 16: MODBUS Register WRITE
Write a number of subsequent registers on the MODBUS address space starting with StAdd.
• Function is implemented in devices Class.Group-Version = 5.20-10.XX and later
• A register contains 2 bytes (16 bit).
• The number of registers written in one cycle is limited to 2 (0x02) for Class.Group-Version = 5.20-10.XX
• Byte-count of the answer will be an even number (1 register = 2 bytes).
• 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.
• Writing float values (0x03XX and 0xFFXX) always requires 2 data registers.
• #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