RM0312 datasheet(208/275 Pages) STMICROELECTRONICS

208 / 275 page

Serial peripheral interface (SPI)

RM0312

208/275

DocID022352 Rev 3

•

In unidirectional receive-only mode (BDM = 0 and RXONLY = 1)

–

The sequence begins as soon as the bit SPE = 1

–

Only the receiver is activated and the received data on MISO pin is shifted in

serially to the 8-bit shift register and then parallel loaded into the SPI_DR register

(Rx Buffer).

•

In bidirectional mode, when transmitting (BDM = 1 and BDOE = 1)

–

The sequence begins when a data is written into the SPI_DR register (Tx buffer).

–

The data is then parallel loaded from the Tx buffer into the 8-bit shift register

during the first bit transmission and then shifted out serially to the MOSI pin.

–

No data is received.

•

In bidirectional mode, when receiving (BDM = 1 and BDOE = 0)

–

The sequence begins as soon as SPE = 1 and BDOE = 0.

–

The received data on MOSI pin is shifted in serially to the 8-bit shift register and

then parallel loaded into the SPI_DR register (Rx Buffer).

–

The transmitter is not activated and no data is shifted out serially to the MOSI pin.

Start sequence in slave mode

•

In full-duplex (BDM=0 and RXONLY=0)

–

The sequence begins when the slave device receives the clock signal and the first

bit of the data on its MOSI pin. The remaining 7 bits are loaded into the shift

–

At the same time, the data is parallel loaded from the Tx buffer into the 8-bit shift

pin. The software must have written the data to be sent before the SPI master

device initiates the transfer.

•

In unidirectional receive-only mode (BDM = 0 and RXONLY = 1)

–

The sequence begins when the slave device receives the clock signal and the first

bit of the data on its MOSI pin. The remaining 7 bits are loaded into the shift

–

The transmitter is not activated and no data is shifted out serially to the MISO pin.

•

In bidirectional mode, when transmitting (BDM = 1 and BDOE = 1)

–

The sequence begins when the slave device receives the clock signal and the first

bit of the Tx buffer is transmitted to the MISO pin.

–

The data is then parallel loaded from the Tx buffer into the 8-bit shift register

during the first bit transmission and then shifted out serially to the MISO pin. The

software must have written the data to be sent before the SPI master device starts

the transfer.

–

no data is received.

•

In bidirectional mode, when receiving (BDM = 1 and BDOE = 0)

–

The sequence starts when the slave device receives the clock signal and the first

bit of the data to its MISO pin.

–

The data received on MISO pin is shifted in serially to the 8-bit shift register and

then parallel loaded into the SPI_DR register (Rx Buffer).

–

The transmitter is not activated and no data is shifted out serially to the MISO pin.

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