CHAPTER 13 RS-485 COMMUNICATIONS
13-12
Modbus RTU Communications
13
(3) Message examples
Shows a message example to write in three pieces of coil data from CONT22 signal.
<Query example>
Station No. 1 byte
01
･･･
When the amplifier station no. is "1".
FC 1 byte
0F
･･･
0Fh
02
Address
2 bytes
15
･･･
Specify 0215h as the CONT22 signal address.
00
No. of coil data
2 bytes
03
･･･
Specify 3 = 0003h as the number of coils.
No. of data bytes
1 byte
01
･･･
The value obtained from 3 pcs/8 and by rounding
up decimal
Information
Data 1
1 byte
06
･･･
See below.
03
CRC check
16 bits
(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
1 (ON)
CONT23
1 (ON)
CONT22
0 (OFF)
<Response message example>
Station No. 1 byte
01
FC 1 byte
0F
02
Address
2 bytes
15
00
Information
No. of coil data
2 bytes
03
05
CRC check
16 bits
(2 bytes)
B6
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