Fujitsu F202RA, MB89202 manual Bidirectional Serial I/O Operation, 335

CHAPTER 14 8-BIT SERIAL I/O

		Figure 14.10-2		Bidirectional Serial I/O Operation
		SIO-A			SIO-B
		START			START
		Stop SIO-A operation			Stop SIO-B operation
		(SST=0)			(SST=0)
		Set SI pin to serial data			Set SI pin to serial data
		input (input port)			input (input port)
	-	Set SCK pin to shift clock			- Set SCK pin to shift clock
		output			input
	-	Set SO pin to serial data			- Set SO pin to serial data
		output			output
	-	Select internal shift clock			- Select external shift clock
	-	Set data transfer (shift			- Select same data transfer
		clock) direction			(shift) direction as SIO-A
		Is SIO-B in			Set output data
NOserial transfer allowance
		state?(*1)
					Allow serial data transfer
			Transfer allowance state
		YES			(SST=1)

Set output data

Start serial I/O transfer(*2)

	(SST=1)
	SIO-A	SIO-B
		Serial data output via SIO-A
	Serial data transfer		Serial data transfer
		Simultaneous data input via SIO-B
NO			NO
	End of 8-bit transfer?		End of 8-bit transfer?
(*3)		(*3)
	YES(SST=0)		YES(SST=0)
	Read input data		Read input data
YES		SST: The SST bit is the serial I/O transfer start bit of the serial mode
	Is next data available?
	NO	register (SMR).

END

*1 If only the SO, SI, and SCK pins are connected, there is no method for directly checking whether SIO-B is in the serial transfer allowance state. For this reason, a timer, etc., must be used to monitor the wait time period that lasts until SIO-B is allowed for transfer via software.

*2 If SIO-B is not allowed for serial I/O transfer, data cannot be transferred correctly even if SIO-A starts serial I/O transfer.

*3 When 8-bit data transfer terminates, a interrupt request occurs.

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