
M0A21/M0A23 Series
May 06, 2022
Page
532
of 746
Rev 1.02
M0
A21
/M
0
A
2
3
SE
RIES
TEC
H
NICAL
RE
FEREN
C
E
M
ANUAL
Half-duplex SPI
Master/Slave
SPI_MOSI
(USCIx_DAT0)
SPI_MOSI
(USCIx_DAT0)
SPI_CLK
(USCIx_CLK)
SPI_SS
(USCIx_CTL0)
SPI Communication Signals
TX Data Word 0
TX Data Word N
Data Frame
SPI_SS
(USCIx_CTL0)
SPI_MOSI
(USCIx_DAT0)
SPI_CLK
(USCIx_CLK)
SPI_MISO
(USCIx_DAT1)
RX Data Word 0
RX Data Word N
Note:
x = 0, 1
Figure 6.14-44-Wire Full-Duplex SPI Communication Signals (Master Mode)
RX Data Word 0
RX Data Word N
Data Frame
SPI_SS
(USCIx_CTL0)
SPI_MOSI
(USCIx_DAT0)
SPI_CLK
(USCIx_CLK)
SPI_MISO
(USCIx_DAT1)
TX Data Word 0
TX Data Word N
Note:
x = 0, 1
Figure 6.14-54-Wire Full-Duplex SPI Communication Signals (Slave Mode)
Serial Bus Clock Configuration
The USCI controller needs the peripheral clock to drive the USCI logic unit to perform the data transfer.
The peripheral clock frequency is equal to PCLK frequency.
In Master mode, the frequency of the SPI bus clock is determined by protocol-relative clock generator.
In general, the SPI bus clock is denoted as SPI clock. The frequency of SPI clock is half of f
SAMP_CLK
,
which can be selected by SPCLKSEL (USPI_BRGEN[3:2]). Refer to section 6.12.4 for details of
protocol-relative clock generator.
In Slave mode, the SPI bus clock is provided by an off-chip Master device. The peripheral clock