R01UH0823EJ0100 Rev.1.00
Page 1375 of 1823
Jul 31, 2019
RX23W Group
38. Serial Peripheral Interface (RSPIa)
38.3.5
Transfer Format
38.3.5.1
CPHA = 0
shows a sample transfer format for the serial transfer of 8-bit data when the SPCMDm.CPHA bit is 0.
Note that clock synchronous operation (the SPCR.SPMS bit is 1) should not performed when the RSPI operates in slave
mode (SPCR.MSTR = 0) and the CPHA bit is 0. In
, RSPCKA (CPOL = 0) indicates the RSPCKA signal
waveform when the SPCMDm.CPOL bit is 0; RSPCKA (CPOL = 1) indicates the RSPCKA signal waveform when the
CPOL bit is 1. The sampling timing represents the timing at which the RSPI fetches serial transfer data into the shift
register. The I/O directions of the signals depend on the RSPI settings. For details, refer to
.
When the SPCMDm.CPHA bit is 0, the driving of valid data to the MOSIA and MISOA signals commences at an SSLAi
signal assertion timing. The first RSPCKA signal change timing that occurs after the SSLAi signal assertion becomes the
first transfer data fetch timing. After this timing, data is sampled at every 1 RSPCK cycle. The change timing for MOSIA
and MISOA signals is 1/2 RSPCK cycles after the transfer data fetch timing. The CPOL bit setting does not affect the
RSPCKA signal operation timing; it only affects the signal polarity.
t1 denotes a period from an SSLAi signal assertion to RSPCKA oscillation (RSPCK delay). t2 denotes a period from the
termination of RSPCKA oscillation to an SSLAi signal negation (SSL negation delay). t3 denotes a period in which
SSLAi signal assertion is suppressed for the next transfer after the end of serial transfer (next-access delay). t1, t2, and t3
are controlled by a master device running on the RSPI system. For a description of t1, t2, and t3 when the RSPI of this
MCU is in master mode, refer to
section 38.3.10.1, Master Mode Operation
Figure 38.22
RSPI Transfer Format (CPHA = 0)
Serial transfer period
1
2
3
4
5
6
7
8
RSPCK
cycle
Start
End
RSPCK
(CPOL = 0)
Sampling
timing
MOSI
MISO
SSLi
t1
t2
t3
RSPCK
(CPOL = 1)
RSPCKA
(CPOL = 0)
RSPCKA
(CPOL = 1)
MOSIA
MISOA
SSLAi