Audio Data [31:0]
DMA Request
Audio FIFO
Audio
Conversion
HDMI
Audio Data Request
REGISTERs
HDMI Core
L3 Interconnect
Preliminary
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Architecture
Figure 6-5. HDMI Audio Interface Overview
6.2.9.2.2 Audio FIFO Overview
The audio FIFO provides buffering to ensure that audio samples can always be delivered to the HDMI
core exactly when required, despite the L3 interconnect latency.
6.2.9.2.2.1 Audio Data Request
By default, the audio FIFO is filled by the device EDMA using a standard DMA request signal mapped
to DSS_HDMI_DMA on the display subsystem level. For additional mapping information, see
The FIFO can also use an IRQ signal (AUDIO_FIFO_SAMPLE_REQ_INTR) to request audio data,
instead of a DMA request, using the same threshold. The IRQ status can be read in the
HDMI_WP_IRQSTATUS[10] AUDIO_FIFO_SAMPLE_REQ_INTR bit. For more information about the
audio IRQ, see
The selection between DMA or IRQ request can be done through the HDMI_WP_AUDIO_CTRL[9]
DMA_OR_IRQ bit.
The audio data is written in the HDMI_WP_AUDIO_DATA[31:0] FIFO_DAT bit field.
The request is made based on comparison of fullness with register programmable thresholds. The
DMA/IRQ is generated when the number of samples (24- or 16-bit) in the FIFO is less than or equal to
the threshold value.
•
The size of samples is selected through the HDMI_WP_AUDIO_CFG[0] SAMPLE_SIZE bit.
•
The valid number of samples can be read from the HDMI_WP_AUDIO_CTRL[25:16].
NUMBER_OF_SAMPLE bit field:
•
The threshold value can be set in the HDMI_WP_AUDIO_CTRL[8:0] TRESHOLD_VALUE bit field.
The DSS_HDMI_DMA signal is released (deactivated) when the last transfer of the DMA burst is
performed in the FIFO. An internal counter is used to do this. The reset value of this counter is set to 16
and the maximum value is set to 64. In this case, the maximum length of the DMA transfer is 64 (32-bit
interface access). The counter can be configured through the HDMI_WP_AUDIO_CFG2[15:8]
DMA_TRANSFER bit field.
The threshold value and the DMA burst size must be set to ensure the filling of the FIFO to four
samples. The minimum level (otherwise, underflow occurs) is four audio samples, which can be 2 ×
32-bit data (in case of two samples per word) or 4 × 32-bit data (IEC or one sample per word). The
interconnect latency must be considered. The number of samples is controlled through the
HDMI_WP_AUDIO_CFG[1] SAMPLE_NBR bit.
709
SPRUGX9 – 15 April 2011
High-Definition Multimedia Interface (HDMI)
© 2011, Texas Instruments Incorporated
Содержание TMS320C6A816 Series
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