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ACK
ENQ
3 seconds
3 seconds
ENQ
ENQ
ENQ
ACK
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.
To phase 2.
Receiving station
Sending station
■ Phase 1 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 an 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.
Sending
station
Receiving
station
To phase 2.
You may modify the number of ENQ iterations for the sending station. The
default is 10 times at three-second intervals. For details, refer to the SET
PROTOCOL screen in System Mode (pp. 54 and 56) and the XFILE statement
given in "BHT-BASIC Programmer's Manual."
TIP