CHAPTER 13 RS-485 COMMUNICATIONS

13

3. Function codes (FC)

The six types of FC below are supported:

Category

FC

Function

Broadcasting

Data manipulation

03h (3)

Read out various data

Disabled

10h (16) Write in various data

Enabled

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

Coil data manipulation 01h (1)

Read out coil data

Disabled

05h (5)

Write in single coil data

Enabled

0Fh (15) Write in coil data

Enabled

Maintenance

08h (8)

Echo back

Disabled

*Queries from master are accepted, and response messages are not returned.

 FC 03h (Readout of various data)

(1) Query from the master

Station No.

1 byte

FC

1 byte

･･･ 03h

Information

Address

No. of registers

2 bytes

2 bytes

(H)

(L)

(H)

(L)

･･･ Specify the data address.

* For the addresses, refer to the table 13-1.

･･･ Specify the number of sets of data n × 2.

* Specify n × 10 on the positioning data.

16 bits (L)

* The max number of positioning data is

CRC check

(2

bytes)

(H)

9, and 45 for others.

(2) Response message from the amplifier

Station No.

FC

No. of data

bytes

1 byte

1 byte

1 byte

･･･ 03h

･･･ n × 4

* The positioning data are n × 20.

Information

Data 1

~

Data n

CRC check

4 bytes

~

4 bytes

16 bits

(2

bytes)

(HH)

(HL)

(LH)

(LL)

(HH)

(HL)

(LH)

(LL)

(L)

(H)

･･･ Readout data for n sets from the specified

address

* The positioning data are 20 bytes per

data.

* For the data format, refer to page 13-14

[Table 13-1].

* "0" is returned to nonexistent data.

13-6 Modbus RTU Communications