R01UH0823EJ0100 Rev.1.00
Page 1405 of 1823
Jul 31, 2019
RX23W Group
38. Serial Peripheral Interface (RSPIa)
(5) Flow of Software Processing
Software processing during clock-synchronous master operation is the same as that for SPI master operation. For details,
refer to
,
. Note that mode fault errors will not occur.
38.3.11.2
Slave Mode Operation
(1) Starting a Serial Transfer
When the SPCR.SPMS bit is 1, the first RSPCKA edge triggers the start of a serial transfer in the RSPI.
When detecting the start of a serial transfer in a condition in which the shift register is empty, the RSPI changes the status
of the shift register to “full”, so that data cannot be copied from the transmit buffer to the shift register when serial
transfer is in progress. If the shift register was full before the serial transfer started, the RSPI keeps the status of the shift
register unchanged, in the full state.
When the SPMS bit is 1, the RSPI drives the MISOA output signal.
For details on the RSPI transfer format, refer to
section 38.3.5, Transfer Format
.
It should be noted that the SSLA0 input signal is not used in clock synchronous operation.
(2) Terminating a Serial Transfer
The RSPI terminates the serial transfer after detecting an RSPCKA edge corresponding to the final sampling timing.
When free space is available in the receive buffer (the SPRF flag is 0), upon termination of serial transfer the RSPI
copies received data from the shift register to the receive buffer of the SPDR register. Upon termination of a serial
transfer the RSPI changes the status of the shift register to “empty” regardless of the receive buffer status. The final
sampling timing changes depending on the bit length of transfer data. In slave mode, the RSPI data length depends on the
SPCMD0.SPB[3:0] bit setting.
For details on the RSPI transfer format, refer to
section 38.3.5, Transfer Format
.