BECKHOFF BK7300 - Manual (Page 28)

MODBUS
24 BK7300
Writing a Digital Output (Function 5)
FORCE SINGLE COIL Function 5 can be used to write a digital output. In this example the third
digital output of slave number 11 is written. The digital outputs begin at
offset 0x0000 (hex). The digital value is located in the high byte of the data.
To switch the output on, "Data high" must contain 0xFF (hex), while 0x00
(hex) is used to switch the output off again. "Data low" must contain 0x00
(hex).
Query
Byte Name Example RTU ASCII
Start frame „:“ 0x3A
Slave address 11 0x0B „0B“ 0x30, 0x42
Function code 5 0x05 „05“ 0x30, 0x35
Start address high 0 0x00 „00“ 0x30, 0x30
Start address low 2 0x02 „02“ 0x30, 0x32
Data high 255 0xFF „FF“ 0x46, 0x46
Data low 0 0x00 „00“ 0x30, 0x32
Error Check
LRC / CRC
0x2D
0x50 „EF“ 0x45, 0x46
End of frame t1-t2-t3 CRLF 0xD, 0xA
Response
The coupler answers with the same telegram.
Byte Name Example RTU ASCII
Start frame „:“ 0x3A
Slave address 11 0x0B „0B“ 0x30, 0x42
Function code 5 0x05 „05“ 0x30, 0x35
Start address high 0 0x00 „00“ 0x30, 0x30
Start address low 2 0x02 „02“ 0x30, 0x32
Data high 255 0xFF „FF“ 0x46, 0x46
Data low 0 0x00 „00“ 0x30, 0x32
Error Check
LRC / CRC
0x2D
0x50 „EF“ 0x45, 0x46
End of frame t1-t2-t3 CRLF 0xD, 0xA