Denso BHT-7500S User Manual page 201

Abnormal termination of phase 2 (Abort of phase 2)
If the sending station receives no ACK from the receiving station after sending an
ENQ nine times in succession, it sends an EOT to the receiving station after 3
seconds from the 9th ENQ to terminate this transmission sequence abnormally.
Phase 3: Release of Data Link
Normal phase 3
The sending station transmits an EOT to the receiving station. Upon receipt of an
ACK from the receiving station, the sending station terminates the message trans-
mission normally and releases the data link.
Sending
station
Normal
termination
Sending
station
3 seconds
ENQ (1)
3 seconds
ENQ (2)
ENQ (9)
3 seconds
EOT
Abnormal
termination
EOT
ACK
181
Appendices
Receiving
station
Receiving
station