Beckhoff BK7300 User Manual download pdf (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

4 LRC

1 2 ... 30 31 32 33 34 35 36 37 38 39 40

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Beckhoff BK7300 User Manual Page 35