Denso BHT-7500S, BHT-7500W user manual Normal phase, Enq

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		ENQ
		ACK
	To phase 2.

Receiving 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

3seconds

3seconds

ENQ

ENQ

ENQ

Receiving station

ACK

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. 62 and 64) and the XFILE statement given in "BHT-BASIC Programmer's Manual."

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