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Rev. 1.00
448 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
21 Serial Peripheral Interface (SPI)
The accompanying figure shows the continuous data transfer timing diagram of this format. Note
that the SEL signal must change to an inactive level between each data frame.
SCK
SEL (SELAP=0)
Data1
Data2
MOSI/MISO
SEL (SELAP=1)
Figure 156. SPI Continuous Data Transfer Timing Diagram – CPOL = 0, CPHA = 0
CPOL = 0, CPHA = 1
In this format, the received data is sampled on the SCK line falling edge while the transmitted
data is changed on the SCK line rising edge. In the master mode, the first bit is driven when data is
written into the SPIDR register. In the slave mode, the first bit is driven at the first SCK clock rising
edge. The accompanying figure shows the single data byte transfer timing.
SCK
MISO
MOSI
TX[7]
TX[6]
TX[5]
TX[4]
TX[3]
TX[2]
TX[1]
TX[0]
RX[7]
RX[6]
RX[5]
RX[4]
RX[3]
RX[2]
RX[1]
½ SCK
SEL(SELAP=1)
RX[0]
Data sampled
SEL(SELAP=0)
Figure 157. SPI Single Byte Transfer Timing Diagram – CPOL = 0, CPHA = 1
The accompanying figure shows the continuous data transfer diagram timing. Note that the SEL
signal must remain active until the last data transfer has completed.
SCK
SEL (SELAP=0)
SEL (SELAP=1)
Data1
Data2
MOSI/MISO
Figure 158. SPI Continuous Transfer Timing Diagram – CPOL = 0, CPHA = 1