Casio WK3800 Instruction Manual - Page 41

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 Data Sender HDR → ← HDS HDA → ← HDS HDA → : : HDA → ← EOD : Other subsessions : ← EOS Operation Send Request (Optional) Data Send Acknowledge Data Send Acknowledge Acknowledge Data End End of session The same packet is resent when a checksum mismatch or incompatible data structure error is detected. Data Receiver Data Sender HDR → ← HDS HDA → ← HDS HDE → ← HDS : : HDE → ← EOD : Other subsessions : ← EOS Operation Send Request (Optional) Data Send Acknowledge Data Send Error Data Resend Error Data End End of session Data send is canceled when no acknowledgement (ACK) is received. 41