CHAPTER 13 RS-485 COMMUNICATIONS
13-6
Modbus RTU Communications
13
3. Function codes (FC)
The six types of FC below are supported:
Category FC Function Broadcasting
03h (3) Read out various data Disabled
10h (16) Write in various data Enabled
Data manipulation
17h (23) Read out/write in various data Enabled*
01h (1) Read out coil data Disabled
05h (5) Write in single coil data Enabled
Coil data manipulation
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
(H)
Address 2 bytes
(L)
･･･
Specify the data address.
* For the addresses, refer to the table 13-1.
(H)
Information
No. of registers 2 bytes
(L)
･･･
Specify the number of sets of data
n × 2
.
* Specify
n × 10
on the positioning data.
(L)
CRC check
16 bits
(2
bytes)
(H)
* The max number of positioning data is
9, and 45 for others.
(2) Response message from the amplifier
Station No. 1 byte
FC 1 byte
･･･
03h
No. of data
bytes
1 byte
･･･
n × 4
* The positioning data are
n × 20
.
(HH)
(HL)
(LH)
Data 1 4 bytes
(LL)
~ ~
(HH)
(HL)
(LH)
Information
Data n 4 bytes
(LL)
･･･
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.
(L)
CRC check
16 bits
(2
bytes)
(H)
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