Handshake Protocol Communication Flow - Casio PX-410R Supplementary Manual

19.3

Handshake Protocol Communication Flow

A session starts with the receiving device sending a request using an HDR or with the sending device sending
HDS 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 (at
least 2000 msec) is treated as a timeout error, and data communication is terminated.
The sending device resends the last data if the receiving device returns an HDE (error) due to checksum mismatch,
incompatible data structure, or some other reason. If an error repeats a number of times (undefined), either the
sending device or the receiving device sends an HDJ to terminate the session.
A session ends after the sending device sends all the parameter sets, and sends a final EOD in response to an
HAD (ACK) from the sending device.
Data Receiver
HDR →
← HDS
HDA →
← HDS
HDA →
:
:
HDA →
← EOD
:
Other subsessions
:
← EOS
The same packet is resent when a checksum mismatch or incompatible data structure error is detected.
Data Receiver
HDR →
← HDS
HDA →
← HDS
HDE →
← HDS
:
:
HDE →
← EOD
:
Other subsessions
:
← EOS
Data send is canceled when no acknowledgement (ACK) is received.
Data Sender
Send Request (Optional)
Data Sender
Send Request (Optional)
Operation
Data Send
Acknowledge
Data Send
Acknowledge
Acknowledge
Data End
End of session
Operation
Data Send
Acknowledge
Data Send
Error
Data Resend
Error
Data End
End of session
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