Causes of SECS-I communication NAK
What NAK means in SECS-I means there is a problem receiving a message. If NAK occurs instead of
ACK:
1) A T1 Timeout occurred while receiving a message.
2) A T2 Timeout occurred while receiving a message.
3) A message was received but the checksum did not match.
If the above occurs, send a NAK and close the message transaction.