CHAPTER 13 RS-485 COMMUNICATIONS

(3) Message examples

Shows a message example to write in three pieces of coil data from CONT22 signal.

<Query example>

Station No.

FC

Address

1 byte

1 byte

2 bytes

No. of coil data

Information

No. of data bytes

2 bytes

1 byte

Data 1

1 byte

01 ･･･ When the amplifier station no. is "1".

0F ･･･ 0Fh

02 ･･･ Specify 0215h as the CONT22 signal address.

15

00 ･･･ Specify 3 = 0003h as the number of coils.

03

01

･･･ The value obtained from 3 pcs/8 and by rounding

up decimal

06 ･･･ See below.

CRC check

16 bits 03

(2 bytes) 74

Data are allocated from LSB in order starting from the smaller address.

The corresponding bit indicates ON with "1" and OFF with "0". The rest of bits are all fixed to "0."

Data1 (=06h)

0

0

0

0

0

CONT24 CONT23 CONT22

1 (ON) 1 (ON) 0 (OFF)

<Response message example>

Station No.

1 byte 01

FC

1 byte 0F

Information

Address

No. of coil data

2 bytes

2 bytes

02

15

00

03

CRC check

16 bits 05

(2 bytes) B6

13

13-12 Modbus RTU Communications