Modbus TCP
A-8
AC30V series Variable Speed Drive
Modbus Exception Codes
Three Modbus exception codes are supported:
ILLEGAL FUNCTION (01)
The Modbus function is not supported by the slave.
ILLEGAL DATA ADDRESS (02)
If the register data address contained in the Modbus request maps to an AC30V parameter that is outside the range of parameter numbers then
this exception will occur.
ILLEGAL DATA VALUE (03)
If the number of bytes or words contained in the Modbus request field is out of range then this exception will occur.
Process Active and Lost Communications Trip
PROCESS ACTIVE FLAG
The Process Active flag is represented by the AC30V parameter
0943 Process Active
. This parameter changes to TRUE on the first valid
Modbus request.
If the parameter
0941 Modbus Timeout
is set to a non-zero value then the
Process Active
parameter will subsequently change to FALSE if a
Modbus request is not received within the timeout period.
TRIP
If enabled, a break in the Modbus communications can be used to generate a trip. The
0943 Process Active
parameter is used to generate the
trip. If this parameter transitions from TRUE to FALSE then a trip will event will be generated.
To enable the base communications Modbus trip, the parameter
0942 Modbus Trip Enable
must be set to TRUE
and
the
BASE MODBUS
BREAK
bit set in the parameter
0697 Enable 1-32
. The parameter
0941 Modbus Timeout
must be set to a value other than zero.
For information on enabling trips see Chapter 10 Trips & Fault Finding.
CONNECTION TIMEOUT
The parameter
1241 Open Connections
indicates the number of open connections to the AC30V Modbus TCP server.
A connection receive timeout may be set using the parameter
1458 Modbus Conn Timeout
. If this is set to a value other than zero, then the
connection will be closed by the server if no data has been received within the timeout period. This is useful, for example, if the link between the
server and client is lost, otherwise the connection may remain open indefinitely.
