Denso BHT-4000 User Manual page 96

Data transmission may accidentally involve various types of errors. The BHT-protocol
is designed to recover from those errors as frequently as possible. What follows is the
BHT-protocol for phases 1 through 3.
Phase 1: Establishment of Data Link
Normal phase 1
The sending station transmits an ENQ to the receiving station. Upon receipt of an
ACK from the receiving station, the sending station shifts to phase 2.
Sending station
To phase 2.
Phase 1 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 ENQ sent, it iterates sending of an ENQ at
three-second intervals up to 10 times.
If the sending station receives an ACK before sending an ENQ ten times, it shifts to
phase 2.
ENQ
ACK
Sending
station ENQ
3 sec.
ENQ
3 sec.
ENQ
ACK
To phase 2.
Receiving
station
86
Receiving station