Exception Responses; Exception Codes - BONFIGLIOLI Vectron Agile Communications Manual

7.3.8

Exception Responses

When the master device sends a request to the inverter it expects a normal response. One of four
possible events can occur from the master's query:
− If the inverter receives the request without a communication error and can handle the query nor-
mally, it returns a normal response.
− If the inverter does not receive the request due to a communication error, no response is returned.
The master will eventually process a timeout condition for the request.
− If the inverter receives the request, but detects a communication error (parity, LRC, CRC, ...), no
response is returned. The master will eventually process a timeout condition for the request.
− If the inverter receives the request without a communication error, but cannot handle it (for exam-
ple, if the request is to read an unknown parameter), the inverter will return an exception re-
sponse informing the client of the nature of the error.
The exception response message has two fields that differentiate it from a normal response:
Function Code Field:
In a normal response, the inverter echoes the function code of the original request in the function
code field of the response. All function codes have a most–significant bit (MSB) of 0 (their values are
all below 0x80 hexadecimal). In an exception response, the inverter sets the MSB of the function code
to 1. This makes the function code value in an exception response exactly 0x80 hexadecimal higher
than the value would be for a normal response. With the function code's MSB set, the master can
recognize the exception response and can examine the data field for the exception code.
Data Field:
In a normal response, the inverter may return data or statistics in the data field (any information that
was requested in the request). In an exception response, the inverter returns an exception code in the
data field. This defines the server condition that caused the exception.
The Exception Codes generated by the inverter are listed in Chapter 7.3.9 "Exception Codes".
7.3.9

Exception Codes

The following exception codes are generated by the inverter:
Code Modbus Name
1 ILLEGAL FUNCTION
2 ILLEGAL DATA
ADDRESS
3 ILLEGAL DATA VALUE
4 SLAVE DEVICE FAILURE − Read or Write Parameter failed
36
Cases when generated by the Inverter
− Function Code unknown
− Subfunction Code unknown (Diagnostics Function)
− No. of Registers field incorrect (must always be 0x01)
− Unknown Parameter or Parameter Data Type mismatch
− Error in dataset of frame
− No. of bytes too small or too large
− Certain fields not set to specific values
The reason for the error can be obtained by reading out Parameter
VABusSST Error Register
Modbus Agile
11.
Protocol
02/2011