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Rev. 1.00
451 of 576
January 28, 2022
32-Bit Arm
®
Cortex
®
-M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253
21 Serial Peripheral Interface (SPI)
21 Serial Peripheral Interface (SPI)
SPI Dual Mode
When in the Master mode, the SPI interface operation can be configured to Dual mode. A more
efficient data transfer can then be implemented by using this Dual mode together with the four
formats described above. In the Dual mode, the SPI data transmission only supports input direction,
that is, the SPI_MOSI pin is also switched from output to an input function. In this way a two-
wire transfer method is formed to read data from an external device synchronously. In addition,
the Dual mode only supports a data length of 16-bit (DFL=0x8). The Dual mode is commonly used
to read data from an external serial SPI Flash. The following figures show the transfer format bit
sequences in the SPI Dual mode.
½
SCK
SEL (SELAP=1)
MOSI
MISO
SCK
Data sampled
SEL (SELAP=0)
RX[14]
RX[12]
RX[10]
RX[8]
RX[7]
RX[15]
RX[13]
RX[11]
RX[9]
DUALEN
RX[6]
RX[5]
RX[4]
RX[3]
RX[2]
RX[1]
RX[0]
Figure 163. SPI Dual Mode Bit Sequence – CPOL = 0, CPHA = 0, DFL = 0x8 (16-bit), MSB
Transmitted First
SCK
MISO
MOSI
SEL(SELAP=1)
SEL(SELAP=0)
DUALEN
RX[6]
RX[4]
RX[2]
RX[15]
RX[7]
RX[5]
RX[3]
RX[1]
RX[13]
RX[12]
RX[11]
RX[10]
RX[9]
RX[8]
RX[0]
RX[14]
Data sampled
½
SCK
Figure 164. SPI Dual Mode Bit Sequence – CPOL = 0, CPHA = 1, DFL = 0x8 (16-bit), MSB
Transmitted First