Casio LK-270 - Manual (Page 34)

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21.3 Handshake Mode Communication Flow
A session starts with the receiving device sending a request using a HBR, or with the sending device sending HBS data.
The sending device does not send the next packet until it receives an ACK from the receiving device. The maximum wait
time of at least 2000 msec is reserved. Failure of a response to arrive within the wait time is treated as a timeout error,
and data communication is terminated.
The receiving devices returns ERR (error) when there is mismatch in the received data checksum or when an incompatible
data format is discovered. When the sending device receives ERR (error) from the receiving device, it resends the last data
sent. If an error repeats a number of times (three times or more for this Instrument), either the sending device or the receiving
device sends an RJC to terminate the session.
A session ends after the sending device transfers the volume of data determined by the number of parameter sets being
transferred, and sends EOD and EOS in response to an ACK from the sending device.
Data Receiver Data Sender Operation
HBR → Send Request (Optional)
← HBS Data Send
ACK → Acknowledge
← HBS Data Send
ACK → Acknowledge
:
:
ACK → Acknowledge
← EOD End of Data
:
Other subsessions
:
← EOS End of Session