CHAPTER 13 RS-485 COMMUNICATIONS

 FC 01h (Read out coil data)

(1) Query from the master

Station No.

1 byte

･･･ 01h

Information

Address

No. of coil data

2 bytes

(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.

CRC check

16 bits (L)

(2 bytes) (H)

(2) Response message form the amplifier

Station No.

No. of data bytes

Information

Data 1

1 byte

･･･ 01h

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

rounding up decimal

(8 bits) ･･･

n pcs data read out from a specified address.

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

* Allocated from LSB in order.

Data N

CRC check

1 byte (8 bits)

16 bits (L)

(2 bytes) (H)

(3) Message examples

Shows a message example to read out ten pieces of coil data from OUT6 signal.

Station No.

1 byte

Address

Information

No. of coil data

2 bytes

CRC check

16 bits

(2 bytes)

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

03 ･･･ Specify 0305h as the OUT6 signal address.

00 ･･･ Specify 10 = 000Ah as the number of coils.

Station No.

1 byte

No. of data bytes 1 byte

Information

Data 1

1 byte

･･･ The value obtained from 10 pcs/8 and by

rounding up decimal

A5 ･･･ See below.

Data 2

1 byte

CRC check

16 bits 43

(2 bytes) 6D

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."

Modbus RTU Communications 13-9