7.7.5.5 DSP and Channel Configuration

The ASRC comprises 4 independent 24-bit DSPs.

Each DSP can be configured to receive/convert/transmit either mono or stereo audio streams.

Each DSP features:

• an input and output sampling frequency defined in the Trigger Selection register (ASRC_TRIG)
• an input and output valid bit per sample defined in registers Valid bit Per Sample In (ASRC_VBPS_IN) and Valid bit Per Sample Out (ASRC_VBPS_OUT)
• transmit and receive FIFOs

Each DSP generates sources of interrupts that can be independently configured with the corresponding Interrupt registers (ASRC_IERx/ASRC_IDRx/ASRC_IMRx/ASRC_ISRx).

The DSP data is written through ASRC_THRx (transmit channels) and the DSP results are read from ASRC_RHRx (receive channels). The number of transfer channels (receive or transmit) equals the number of DSPs.

Each transfer channel can be configured to access one or more DSP.

This configurable function allows concatenation of multiple audio streams transferred with different transmit channels into a single audio stream transferred on a single receive channel. It also allows the split of a single audio stream transferred with a transmit channel into several separate audio streams transferred on several receive channels.

The transfer channel management generates internal trigger events to interface with DMA controller.

The source of interrupts from the transfer channel management are mapped in the status registers together with the DSP sources of interrupt.

The ASRC generates a single interrupt line that may be driven by all DSP status registers.