Casio LK-270 - Manual (Page 35)

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The packed with the same packet number is resent when a checksum mismatch or incompatible data format error is detected.
Session terminates if ERR is detected a number of times.
Data Receiver Data Sender Operation
HBR → Send Request (Optional)
← HBS Data Send
ACK → Acknowledge
← HBS Data Send 1
ERR → Error
← HBS Data Send 2 (Retry 1)
ERR → Error
← HBS Data Send 3 (Retry 2)
ACK → Acknowledge
:
:
ACK → Acknowledge
← EOD End of Data
:
Other subsessions
:
← EOS End of Session
Data Receiver Data Sender Operation
HBR → Send Request (Optional)
← HBS Data Send
ACK → Acknowledge
← HBS Data Send
(Error generated)
ERR → Error
← HBS Data Send (Retry 1)
(Error generated)
ERR → Error
← HBS Data Send (Retry 2)
(Error generated)
ERR → Error
← HBS Data Send (Retry 3)
(Error generated)
RJC → Session stopped