CHAPTER 13 RS-485 COMMUNICATIONS

13

13.1.2 Communication Specifications

Item

Electric I/F

Communication

speed

Specifications

RS-485

38400／19200／9600／115200 bps

Remarks (PA is a parameter No.)

Set by parameter PA2_73

Synchronization

method

Asynchronous (UART)

Communication

Semi-duplex communication

method

Transmission format

Connection cable

Master-slave (servo amplifier) = 1:N

(1N31)

LAN cable (straight) or equivalent

Max. 31 units connected

simultaneously

Cable length

(recommneded)

Entire extended length:

100 m or less (up to 38400 bps)

40 m or less (115200 bps)

Length between stations:

20 m or less

Terminator treatment Master side

Slave side

:100 Ω

recommended

: Unnecessary

Character

configuration

Start bit

Data length

Parity

Stop bit

: 1 bit

: 8 bits

: Even/Odd/None

: 1 or 2 bits

Set by parameter PA2_93

Communications

protocol

Compliant with Modbus RTU protocol

Communications

mode

RTU mode

The ASCII mode is not

supported.

Station number

0: Broadcast

1-31: Slave station No.

Set by parameter PA2_72

Function code (FC)

1(01h): Read out coil data

3(03h): Read out various data

5(05h): Write in single coil data

8(08h): Maintenance (echo back)

15(0Fh): Write in coil data

16(10h): Write in various data

23(17h): Read out/write in various data

Responses other than those in

the left cell are exceptional

responses (improper FC).

Error check method CRC-16 method

Message length

Variable length

Max. 200 bytes

Frame

synchronization

method

Timing synchronization

Frames are initialized if time

data for three characters are

absent.

It is recommended to use the RS-232C - RS-422 converter (model: NW0H-CNV) for the use of 1:1

communications between the master and the slave (servo amplifier). Do not use it for multiple unit

connection.

13-4 Modbus RTU Communications