Denso BHT-200QW Spezifikationen Seite 468

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18.2.4 Programming Notes
18.2.4.1 Retransmission control in serial communications
Any system design using wireless communications must assume data losses due to line
quality deterioration and data duplication due to delays during transmission. If the user
program does not use the BHT protocol, the BHT-Ir protocol, or TCP/IP, it must implement its
own protocol providing retransmission and flow control.
The following gives an example of such retransmission control for a user program.
The frequency of such communications errors varies considerably with the operating
environment and usage conditions, so base the retransmission count and other parameters
on thorough testing in a worst-case environment.
Extended function BT.FN3 function number .fcBTChkSnd allows the user program to check
whether all data messages transmitted actually reached the other end.
BHT
Data message (SN = 2)
Transmission
completion message
Erro
r
Data message (SN = 2)
(sent again)
Same SN means data duplication
Data message (SN = 1)
Transmission
completion message
Error in transmission
completion message
SN = sequence number
Transmission
completion message
Disconnect and close
Retransmission
Other end
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