Beckhoff BC9000 Documentation page 69

Query
Byte name
Function code
Start address high
Start address low
Count high
Count low
The fieldbus coupler answers with byte count 4, i.e. 4 bytes of data are returned. The query was for two
analog channels, and these are distributed over two words. In the analog output process image, the first
channel has the value 0x3FFF, while the second channel has the value 0x0.
Response
Byte name
Function code
Byte count
Data 1 high byte
Data 1 low byte
Data 2 high byte
Data 2 low byte
7.5.4.5 Read input register (Function 4)
The function Read input register reads the inputs on a word basis.
In this example the first two analog inputs (or the first two input words) are read. The analog inputs (or input
words) start at an offset of 0x0000. The length indicates the number of words to be read. A KL3002, for
example, has two words of input data. Therefore, the length to be entered at Number low is two.
Query
Byte name
Function code
Start address high
Start address low
Count high
Count low
The fieldbus coupler answers with byte count 4, i.e. four bytes of data are returned. The query was for two
analog channels, and these are now distributed over 2 words. In the analog input process image, the first
channel has the value 0x0038, while the second channel has the value 0x3F1B.
Response
Byte name
Function code
Byte count
Data 1 high byte
Data 1 low byte
Data 2 high byte
Data 2 low byte
BC9000 and BC9100
Sample
3
8
0
0
2
Sample
3
4
63
255
0
0
Sample
4
0
0
0
2
Sample
4
4
0
56
63
11
Version: 4.0.0
Fieldbus system
69