Denso BHT-7500S User Manual page 200

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.
normally, the transmission results in an abnormal end.
Sending
station
Phase 2 with iterated ENQ transmission due to no response or invalid
response
If the sending station receives no response or any invalid response from the
receiving station in response to a 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 seconds
ENQ
3 seconds
ENQ
ACK
Data text m+1
180
Even if phase 3 terminates
Receiving
station
Receiving
station