User`s manual

21
FX3U Series Programmable Controllers
User’s Manual - MODBUS Serial Communication Edition
4 Wiring
4.2 Selecting Connection Method
1
Outline
2
Specifications
3
System Configuration
4
Wiring
5
Communication Setup
6
Related Devices and Comm. Status
7
MODBUS Standard Commands
8
Master Specification
9
Slave Specification
10
Creating Programs
4.2 Selecting Connection Method
When using MODBUS serial communication, communication can be achieved in accordance with MODBUS
RS-232C or RS-485. For the FX
3U, only one channel can be used for MODBUS serial communication,
Master or Slave.
4.2.1 For communication in accordance with MODBUS RS-232C (1-to-1 connection)
For communication in accordance with MODBUS RS-232C, 1-to-1 connection is possible. Make sure that the
total extension distance is 15m (49'2") or less.
4.2.2 For communication in accordance with MODBUS RS-485 (1-to-N connection)
For communication in accordance with MODBUS RS-485, up to 16 PLC Slave Nodes can be connected to
one Master Node. Make sure that the total extension is 500m (1640'5") or less.
Note
MODBUS Slave Nodes do not need to be numbered in any specific order.
Communication
equipment operating
in accordance with
MODBUS RS-232C
Communication
equipment operating
in accordance with
MODBUS RS-232C
FX PLC FX PLC
Master station
Slave station No. 1 (01H)
++
15 m (49' 2")
Communication
equipment operating
in accordance with
MODBUS RS-485
Communication
equipment operating
in accordance with
MODBUS RS-485
Communication
equipment operating
in accordance with
MODBUS RS-485
FX PLC FX PLC
FX PLC
Master station
Slave station No. 1 (01H)
500 m (1640' 5")
+++
.......
Slave station No. 16 (10H)