BC7300
45
Query
Byte Name
Example
RTU
Description
Slave address
11
0x0B
Function code
4
0x04
Start address high
0
0x00
Start address low
0
0x00
Count high
0
0x00
Count low
2
0x02
Number of data words
Error Check
LRC / CRC
0x71
0x61
End of frame
t1-t2-t3
Response
The Bus Terminal Controller answers with byte count 4, i.e. 4 bytes of data
are returned. The query was for 2 input words, and these are now
distributed over 4 bytes.
Byte Name
Example
RTU
Description
Start frame
Slave address
11
0x0B
Function code
4
0x04
Count byte
4
0x04
Number of data bytes
Data 1 high byte
0
0x00
Address %QB129
Data 1 low byte
56
0x38
Address %QB128
Data 2 high byte
63
0x3F
Address %QB131
Data 2 low byte
11
0x0B
Address %QB130
Error Check
LRC / CRC
0x80
0x7E
End of frame
t1-t2-t3