Serial peripheral interface (SPI) RM0008
696/1096 Doc ID 13902 Rev 12
As a security, hardware does not allow the setting of the SPE and MSTR bits while the
MODF bit is set.
In a slave device the MODF bit cannot be set. However, in a multimaster configuration, the
device can be in slave mode with this MODF bit set. In this case, the MODF bit indicates that
there might have been a multimaster conflict for system control. An interrupt routine can be
used to recover cleanly from this state by performing a reset or returning to a default state.
Overrun condition
An overrun condition occurs when the master device has sent data bytes and the slave
device has not cleared the RXNE bit resulting from the previous data byte transmitted.
When an overrun condition occurs:
● the OVR bit is set and an interrupt is generated if the ERRIE bit is set.
In this case, the receiver buffer contents will not be updated with the newly received data
from the master device. A read from the SPI_DR register returns this byte. All other
subsequently transmitted bytes are lost.
Clearing the OVR bit is done by a read from the SPI_DR register followed by a read access
to the SPI_SR register.
CRC error
This flag is used to verify the validity of the value received when the CRCEN bit in the
SPI_CR1 register is set. The CRCERR flag in the SPI_SR register is set if the value
received in the shift register does not match the receiver SPI_RXCRCR value.
25.3.11 SPI interrupts
Table 181. SPI interrupt requests
Interrupt event Event flag Enable Control bit
Transmit buffer empty flag TXE TXEIE
Receive buffer not empty flag RXNE RXNEIE
Master Mode fault event MODF
ERRIEOverrun error OVR
CRC error flag CRCERR
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