CHAPTER 13 RS-485 COMMUNICATIONS

<Response message example>

Station No.

1 byte

01

FC

1 byte

05

Information

Address

No. of coil data

2 bytes

2 bytes

02

08

FF

00

CRC check

16 bits 0C

(2 bytes) 40

 FC 0Fh (Write in coil data)

(1) Query from the master

Station No.

FC

Address

No. of coil data

Information No. of data bytes

Data 1

~

Data N

1 byte

1 byte

2 bytes

2 bytes

1 byte

1 byte

~

1 byte

･･･ 0Fh

(H) ･･･ Specify the coil address.

(L)

* For the addresses, refer to the table 13-4.

(H) ･･･ Specify the number of coils n.

(L)

* Up to 16 pcs.

･･･ The value (N) obtained from n/8 and by

rounding up decimal

(8 bits)

･･･ n pcs of data read out from a specified

address.

* 1 pcs = 1 bit (1 byte by 8 pcs)

(8 bits)

* Allocated from LSB in order.

CRC check

16 bits (L)

(2 bytes) (H)

(2) Response message from the amplifier

Station No.

1 byte

FC

1 byte

Information

Address

No. of coil data

2 bytes

2 bytes

(H)

(L)

(H)

(L)

CRC check

16 bits (L)

(2 bytes) (H)

･･･ 05h

･･･ Specified address.

･･･ The number of coils actually written in is m pcs.

* Cannot write in to nonexistent coil data.

13

Modbus RTU Communications 13-11