Denso BHT-4000 User Manual page 100

Phase 2 with EOT
If the sending station receives an EOT anytime during phase 2, it shifts to phase 3 to
terminate the message transmission abnormally. Even if the phase 3 terminates
normally, the transmission results in an abnormal end.
Sending
station
Phase 2 with no response or invalid response
If the sending station receives no response or any invalid response from the
receiving station in response to the transmission block sent, it iterates sending of
an ENQ at three-second intervals up to nine times.
If the sending station receives an ACK before sending an ENQ nine times, it
continues the subsequent message transmission.
Sending
station
EOT
Occurrence of
an error
To phase 3.
Data text m
3 sec.
ENQ
3 sec.
ENQ
ACK
Data text m+1
90
Receiving
station
Receiving
station