IDEC FT1A Series - Page 279

S MART AXIS P RO /L ITE U SER ' S M ANUAL FT9Y-B1378 11-15
11: M ODBUS C OMMUNICATION
Function Code 06 (Preset Single Register)
Function code 06 changes word device data of D (data register).
Communication Frame
Request from Modbus Master
ACK Reply from Modbus Slave
NAK Reply from Modbus Slave
Communication Example
• RTU Mode
Slave No. Function Code Address New Data
xxh 06h xxxxh xxxxh
Slave No. Function Code Address
Acknowledge
Data
xxh 06h xxxxh xxxxh
Slave No. Function Code Error Code
xxh 86h xxh
Purpose
Write 8000 to data register D1708.
D1708 → (1708 – 0) + 400001 = 401709
Modbus address: 401709
Extract lower 5 digits → 1709
1709 – 1 = 1708 = 6ACh
Communication frame address: 06ACh
Condition Slave No. 8
Request from Modbus Master 08 06 06AC 1F40 (CRC)
ACK Reply from Modbus Slave 08 06 06AC 1F40 (CRC)
NAK Reply from Modbus Slave 08 86 xx (CRC)