Serial peripheral interface (SPI) RM0008
711/1128 DocID13902 Rev 15
Figure 246. Transmission using DMA
Figure 247. Reception using DMA
0xF1
Tx buffer
TXE flag
0xF2
BSY flag
0xF3
set by hardware
clear by DMA write
set by hardware
cleared by DMA write
set by hardware
set by hardware
SCK
reset
Example with CPOL=1, CPHA=1
(write to SPI_DR)
MISO/MOSI (out)
DATA 1 = 0xF1
DATA 2 = 0xF2
DATA 3 = 0xF3
software configures the
DMA SPI Tx channel
to send 3 data items
and enables the SPI
DMA writes to SPI_DR
DMA request
ignored by the DMA because
DMA TCIF flag
set by hardware clear by software
DMA writes
DATA1 into
SPI_DR
by hardware
DMA writes
DATA2 into
SPI_DR
DMA writes
DATA3 into
SPI_DR
software waits until BSY=0
(DMA transfer complete)
DMA transfer is
complete (TCIF=1 in
DMA_ISR)
software waits
until TXE=1
DMA transfer is complete
b0 b1 b2 b3 b4 b5 b6 b7 b0 b1 b2 b3 b4 b5 b6 b7
b0 b1 b2 b3 b4 b5 b6 b7
ai17349
MISO/MOSI (in)
DATA 1 = 0xA1
software configures the
DMA SPI Rx channel
to receive 3 data items
and enables the SPI
SCK
DATA 2 = 0xA2
DATA 3 = 0xA3
Example with CPOL=1, CPHA=1
RXNE flag
Rx buffer
set by hardware
(read from SPI_DR)
0xA1 0xA2 0xA3
DMA request
DMA reads
DATA3 from
SPI_DR
flag DMA TCIF
set by hardware
clear
by software
DMA read from SPI_DR
The DMA transfer is
complete (TCIF=1 in
DMA_ISR)
DMA reads
DATA2 from
SPI_DR
DMA reads
DATA1 from
SPI_DR
(DMA transfer complete)
b0 b1 b2 b3 b4 b5 b6 b7 b0 b1 b2 b3 b4 b5 b6 b7 b0 b1 b2 b3 b4 b5 b6 b7
clear by DMA read
ai17350
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