B&B Electronics MODSCAN32 - Manual - Manual (Page 16)

16
Exception Responses
Programming or operation errors are those involving illegal data in a message, no response from the PLC to
its interface unit, or difficulty in communicating with a slave. These errors result in an exception response
from either the master computer software or the PLC slave, depending on the type of error. The exception
response codes are listed below. When a PLC slave detects one of these errors, it sends a response message
to the master consisting of the slave address, function code, error code, and error check fields. To indicate
that the response is a notification of an error, the high-order bit of the function code is set to one.
CODE NAME MEANING
01 ILLEGAL FUNCTION The message function received is not an allowable
action for the addressed slave.
02 ILLEGAL DATA ADDRESS The address referenced in the data field is not an
allowable address for the addressed slave device.
03 ILLEGAL DATA VALUE The value referenced in the data field is not allowable
in the addressed slave location.
04 FAILURE IN ASSOCIATED
DEVICE The slave’s PC has failed to respond to a message or an
abortive error occurred.
05 ACKNOWLEDGE The slave PLC has accepted and is processing the long
duration program command.
06 BUSY, REJECTED
MESSAGE The message was received without error, but the PLC is
engaged in processing a long duration program
command.
07 NAK-NEGATIVE
ACKNOWLEDGMENT The PROGRAM function just requested could not be
performed.