BECKHOFF BK7300 - Manual (Page 35)

MODBUS
BK7300 31
BK7300 Error Answers
EXCEPTION RESPONSE When the user sends the slave either a request or information that the
coupler does not understand, the BK7300 responds with an error report.
This answer contains the function and the error code. 0x80 is added to the
value returned by the function.
Code Name
Meaning
1 ILLEGAL FUNKTION Function not implemented
2 ILLEGAL DATA ADDRESS Invalid address or length
3 ILLEGAL DATA VALUE Invalid parameter
• Diagnostic
functions
• Incorrect number of read/write
accesses to the register
4 SLAVE DEVICE ERROR Watchdog or K-bus error
Example The following example contains an invalid "Start address".
Query
BYTE Contents
Example
1 Slave address 0B
2 Function 01
3 Start address high 0D
4 Start address low FF
5 Data high FF
6 Data low 01
7 LRC
The slave's answer contains the function plus 0x80, together with error
code "02", i.e. an invalid address.
Response
BYTE Contents
Example
1 Slave address 0B
2 Function 81
3 Error code 02
s
4 LRC