Serial audio interface (SAI) RM0440
1824/2126 RM0440 Rev 4
The OVRUDR flag is cleared when COVRUDR bit is set in the SAI_xCLRFR register.
Figure 627. Overrun detection error
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.
Figure 628. FIFO underrun event
MS192348V2
sck
data
Slot 0 ON
Example: FIFO overrun on Slot 1
Audio frame Audio frame
Slot n ON
... ON
FIFO full
OVRUDR
Slot 1 ON Slot 1 ON Slot 0 ON Slot 1 ON
Received data discarded
Data stored again in FIFO
COVRUDR = 1
MS192347V2
sck
data
Slot 0 ON MUTE
Slot size = data size
SD (output)
Example: FIFO underrun on Slot 1
Audio frame Audio frame
MUTE Slot 1 ON ... ON Slot 0 ON
OVRUND=1
MUTE
FIFO empty
OVRUND
To Next Page
Loading...
Need help?
General
