IDEC FT1A Series User Manual

S MART AXIS P RO /L ITE U SER ' S M ANUAL FT9Y-B1378 11-13
11: M ODBUS C OMMUNICATION
Function Code 03 (Read Holding Registers) and Function Code 04 (Read Input Registers)
Function code 03 reads word device data of D (data register), T (timer preset value), or C (counter preset value). One through 64
consecutive words can be read out.
Function code 04 reads word device data of T (timer current value) or C (counter current value). One through 64 consecutive
words can be read out.
Communication Frame
Request from Modbus Master
ACK Reply from Modbus Slave
NAK Reply from Modbus Slave
Communication Example
• RTU Mode
Purpose
Read 2 words starting at data register D1710.
D1710 → (1710 – 0) + 400001 = 401711
Modbus address: 401711
Extract lower 5 digits → 1711
1711 – 1 = 1710 = 6AEh
Communication frame address: 06AEh
Condition
Slave No. 8
D1710 data: 1234h
D1711 data: 5678h
Request from Modbus Master 08 03 06AE 0002 (CRC)
ACK Reply from Modbus Slave 08 03 04 12 34 56 78 (CRC)
NAK Reply from Modbus Slave 08 83 xx (CRC)
Slave No. Function Code Address No. of Words
xxh 03h / 04h xxxxh xxxxh
Slave No. Function Code Quantity of Data First High Byte First Low Byte Last Low Byte
xxh 03h / 04h xxh xxh xxh xxh
Slave No. Function Code Error Code
xxh 83h / 84h xxh

IDEC FT1A Series Specifications

General

Brand	IDEC
Model	FT1A Series
Category	Controller
Language	English