Figure 627. Overrun Detection Error; Figure 628. Fifo Underrun Event - ST STM32G4 Series Reference Manual

Serial audio interface (SAI)
The OVRUDR flag is cleared when COVRUDR bit is set in the SAI_xCLRFR register.
data
FIFO full
OVRUDR
Underrun
An underrun may occur when the audio block in the SAI is a transmitter and the FIFO is
empty when data need to be transmitted. If an underrun is detected, the slot number for
which the event occurs is stored and MUTE value (00) is sent until the FIFO is ready to
transmit the data corresponding to the slot for which the underrun was detected (refer to
Figure 628). This avoids desynchronization between the memory pointer and the slot in the
audio frame.
The underrun event sets the OVRUDR flag in the SAI_xSR register and an interrupt is
generated if the OVRUDRIE bit is set in the SAI_xIM register. To clear this flag, set
COVRUDR bit in the SAI_xCLRFR register.
The underrun event can occur when the audio subblock is configured as master or slave.
SD (output)
FIFO empty
OVRUND
1824/2126

Figure 627. Overrun detection error

Audio frame
sck
Slot 0 ON Slot 1 ON Slot 1 ON Slot 0 ON

Figure 628. FIFO underrun event

Audio frame
sck
data
Slot 0 ON MUTE
Example: FIFO overrun on Slot 1
Received data discarded
Example: FIFO underrun on Slot 1
Slot size = data size
MUTE MUTE
OVRUND=1
RM0440 Rev 4
Audio frame
Slot 1 ON ... ON
Data stored again in FIFO
COVRUDR = 1
Audio frame
Slot 1 ON ... ON Slot 0 ON
RM0440
Slot n ON
MS192348V2
MS192347V2