The following table lists the DisplayPort Audio registers.
| Offset | Access Type | Description |
|---|---|---|
| 0x300 | R/W | TX_AUDIO_CONTROL. Enables audio stream packets in the main link
and provides buffer control. [19]: Set to 1 to mute the audio over link for MST STREAM 4. Not applicable for SST. [18]: Set to 1 to mute the audio over link for MST STREAM 3. Not applicable for SST. [17]: Set to 1 to mute the audio over link for MST STREAM 2. Not applicable for SST. [16]: Set to 1 to mute the audio over link for SST. in MST, set to 1 to mute the Audio on STREAM 1 [5:4]: MST Audio Stream number. This determines which MST stream's link slots carry the input data from the Audio AXI4-Stream Interface. Note: There is only single audio
stream input interface to the subsystem. These bits are not applicable for
SST.
[3]: Audio Enable for STREAM 4 in MST. Not applicable for SST [2]: Audio Enable for STREAM 3 in MST. Not applicable for SST. [1]: Audio Enable for STREAM 2 in MST. Not applicable for SST. [0]: Audio Enable for SST. In MST, Audio Enable for STREAM 1. |
| 0x304 | R/W | TX_AUDIO_CHANNELS. Used to input active channel count.
Transmitter collects audio samples based on this information. [2:0] Channel Count |
| 0x308 | WO | TX_AUDIO_INFO_DATA. The IP can receive and buffer up to four Info Frames before they are processed and sent over the DP Link. The bits in register offset 0x6A0 indicate a full/overflow status of the internal "Info Frame Buffer", which holds these four Info Frames. [31:0] Word of each Info Frame is formatted as per CEA 861-C Info Frame. Total of eight words per each Info Frame must be written in the following order: First word -
Second word - DB3,DB2,DB1,DB0 .... Eighth word - DB27,DB26,DB25,DB24 The data bytes DB1...DBN of CEA Info frame are mapped as DB0-DBN-1. No protection is provided for wrong operations by software. The capability to hold multiple Info Frames is useful in scenarios in which "Info Frames" corresponding to different features (such as Audio and HDR) are to be supported. |
| 0x328 | R/W | TX_AUDIO_MAUD. M value of audio stream as computed by
transmitter. [23:0] = Unsigned value computed when audio clock and link clock are synchronous. |
| 0x32C | R/W | TX_AUDIO_NAUD. N value of audio stream as computed by
transmitter. [23:0] = Unsigned value computed when audio clock and link clock are synchronous. |
| 0x330 to 0x350 | WO | TX_AUDIO_EXT_DATA. [31:0] = Word formatted per Extension packet described in protocol standard. Extended packet is fixed to 32 Bytes length. The controller has buffer space for only one extended packet. Extension packet address space can be used to send the audio Copy management packet/ISRC packet/VSC packets. TX is capable of sending any of these packets. VSC/EXT packets must use the same address space. Nine words must be written in following order: First word -
Second word - DB3,DB2,DB1,DB0 .... Ninth word - DB31, DB30, DB29, DB28 See the DisplayPort Standard for HB* definition. No protection is provided for wrong operations by software. This is a key-hole memory. So, nine writes to this address space is required. |
| 0x6A0 | RO | TX_AUDIO_INFO_FRAME_BUFFER_STATUS. Indicates full/overflow status of the internal Info Frame buffer which can hold up to 4 Info Frames (each of size 8 bytes as mentioned in the description of 0x308 register) received through offset register 0x308, those are to be processed by the IP. For information about “Info Frame”, see the description of TX_AUDIO_INFO_DATA at offset register 0x308. [0] = Internal Info Frame buffer “Full” status.
[1] = Internal Info Frame buffer “Overflow” status.
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