Casio CTK-4200 manual 33

Data Receiver		Data Sender	Operation
(External Device)		(This Instrument)
HBR	----->		Send Request
			(Optional)
ACK	----->		Acknowledge
	<-----	HBS	Data Send
ACK	----->		Acknowledge
	<-----	HBS	Data Send
	:
	:
	(Terminate operation)
	<-----	RJC	Data Send
			Canceled

BSY is returned to the external device when OBS, OBR, HBS, or HBR is sent while the Instrument mode is not suitable to perform bulk dump, etc. After BSY is received, the external device should wait until the instrument enters a mode in which the session is enabled.

Data Receiver		Data Sender	Operation
(External Device)		(This Instrument)
OBR	----->		Send Request
	<-----	BSY	Send Rejected
Data Receiver		Data Sender	Operation
(External Device)		(This Instrument)
	<-----	OBS	Data Send
BSY	----->		Receive Rejected
Data Receiver		Data Sender	Operation
(External Device)		(This Instrument)
HBR	----->		Send Request
	<-----	BSY	Send Rejected
Data Receiver		Data Sender	Operation
(External Device)		(This Instrument)
	<-----	HBS	Data Send
BSY	----->		Receive Rejected

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