ST72344S2 datasheet(120/247 Pages) STMICROELECTRONICS

120 / 247 page

On-chip peripherals

ST72344xx, ST2345xx

120/247

Doc ID 12321 Rev 6

Note:

While the SPIF bit is set, all writes to the SPIDR register are inhibited until the SPICSR

The SPIF bit can be cleared during a second transmission; however, it must be cleared

before the second SPIF bit in order to prevent an Overrun condition (see Overrun condition

(OVR)).

11.4.4

Clock phase and clock polarity

Four possible timing relationships may be chosen by software, using the CPOL and CPHA

bits (See Figure 60).

Note:

The idle state of SCK must correspond to the polarity selected in the SPICSR register (by

pulling up SCK if CPOL = 1 or pulling down SCK if CPOL = 0).

The combination of the CPOL clock polarity and CPHA (clock phase) bits selects the data

capture clock edge.

Figure 60 shows an SPI transfer with the four combinations of the CPHA and CPOL bits.

The diagram may be interpreted as a master or slave timing diagram where the SCK pin, the

MISO pin and the MOSI pin are directly connected between the master and the slave

device.

Note:

If CPOL is changed at the communication byte boundaries, the SPI must be disabled by

resetting the SPE bit.

ST72344S2 Datasheet(PDF) 120 Page - STMicroelectronics