Spi Dual Mode; Figure 163. Spi Dual Mode Bit Sequence - Cpol = 0, Cpha = 0, Dfl = 0X8 (16-Bit), Msb Transmitted; Figure 164. Spi Dual Mode Bit Sequence - Cpol = 0, Cpha = 1, Dfl = 0X8 (16-Bit), Msb Transmitted - Holtek HT32F54231 User Manual

32-Bit Arm ® Cortex ® -M0+ MCU
HT32F54231/HT32F54241/HT32F54243/HT32F54253

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.
DUALEN
SEL (SELAP=0)
SEL (SELAP=1)
½
SCK
SCK
MOSI RX[6]
MISO RX[7]
Data sampled
Figure 163. SPI Dual Mode Bit Sequence – CPOL = 0, CPHA = 0, DFL = 0x8 (16-bit), MSB
Transmitted First
DUALEN
SEL(SELAP=0)
SEL(SELAP=1)
½
SCK
SCK
MOSI
MISO
Figure 164. SPI Dual Mode Bit Sequence – CPOL = 0, CPHA = 1, DFL = 0x8 (16-bit), MSB
Transmitted First
Rev. 1.00
RX[4] RX[2] RX[0]
RX[5] RX[3] RX[1]
RX[6] RX[4] RX[2]
RX[7] RX[5] RX[3]
Data sampled
451 of 576
RX[14] RX[12] RX[10]
RX[15] RX[13] RX[11]
RX[0] RX[14] RX[12] RX[10]
RX[1] RX[15] RX[13] RX[11]
RX[8]
RX[9]
RX[8]
RX[9]
January 28, 2022