Video data received from a display controller can be forwarded to a display sink natively over a Type-C connector by the DP TX controller either in Alt Mode (USB traffic only) or simultaneously with USB traffic in x1 or x2 configuration.
A DisplayPort TX 1.4 controller will support up to four streams of video up to a max resolution of 4K@30fps or a single stream of 8Kp30. It will also support HDCP 2.3. DP TX can be used as x1, x2, or x4 link over a Type-C connector either in Alt Mode or simultaneously with USB traffic in x1 or x2 configuration. DP TX 1.4 max raw bandwidth is 32.4 Gb/s (effective B/W of 25.92 Gb/s) when all lanes are used.
Some of the key features of the DP controller are summarized as follows:
- Support for DisplayPort source (TX) transmissions
- Supports multi-stream transport (MST) and single stream transport (SST)
- Supports multi-pixel mode for 8K/10K video
- Dynamic lane support (1, 2, or 4 lanes)
- Dynamic link rate support (1.62/2.7/5.4/8.1 Gb/s)
- Dynamic support for 6, 8, 10, 12, or 16 bits per component (BPC)
- Dynamic support for RGB/YCbCr444/YCbCr422/YCbCr420 color formats
- Supports 2 to 8 channel audio with 32KHz-192KHz sample rates
- Supports HDCP 2.3 encryption
The following are the main interfaces to the DP TX IP:
Video Pixel Interface
This is a parallel video input interface. The DP TX IP can be configured in either single pixel mode or multi-pixel mode. In single pixel mode, the interface is 48-bits wide (16 bits wide x 3 channels). It also includes a pixel clock (max clock rate of 600 MHz), hsync, vsync, and enable signals. For 8K support, quad pixel mode is required. In quad pixel mode, the video interface as described above is quadrupled.
The DP IP shall support up to four streams (MST mode) and within each stream it can support a multi-pixel mode (single, dual, or quad pixel mode). In MST mode, each stream can have different resolution and timing. For each stream the video pixel interface can be single, dual, or quad pixel mode. The following table shows the stream configuration and the corresponding supported pixel modes.
| Mode | Number of Streams | Pixel Mode in DP |
|---|---|---|
| Functional Mode | VP0,VP1-Live/Nonlive/Mixed mode | S1-Single Pixel Mode |
| Bypass Mode | 4 active streams from PL | S1,S2,S3,S4 all in Single Pixel Mode |
| 2 active streams from PL | S1, S2-Dual Pixel Mode | |
| 1 active stream from PL | S1-Quad Pixel Mode | |
| 1 active stream from PL | S1-Dual Pixel Mode | |
| 1 active stream from PL | S1-Single Pixel Mode |
| Mode | Resolution/Frame Rate | H | V | Refresh (Hz) | pixel/sec | 1ppc (MHz) | 2ppc (MHz) | 4ppc (MHz) | # of streams |
|---|---|---|---|---|---|---|---|---|---|
| Bypass Mode | 8kp30 | 7680 | 4320 | 30 | 995328000 | X | X | 300 | 1 |
| Bypass Mode | 4kp120 | 3840 | 2160 | 120 | 995328800 | X | 600 | 300 | 1 |
| Functional Mode | 4kp60 | 3840 | 2160 | 60 | 497664000 | 600 | 300 | 150 | 2 |
| Functional Mode | 4kp30 | 3840 | 2160 | 30 | 248832000 | 300 | 150 | 75 | 4 |
Audio Interface
DP TX IP supports I2S audio input interface. I2S was chosen as the audio interface option. This interface requires two sets of clocks: the sampling frequency clock and a second clock which is 512 times the sampling frequency. In addition, there are four data signals which carry up to eight channels worth of audio data. In quad pixel mode where four streams are selected, four such interfaces are required.
SDP Interface
This interface is used to input secondary data packets that will be transmitted as part of the video stream. This is a 288-bit data interface and eight control signals. In quad pixel mode, four such interfaces are required.
HDCP Interface
There are two distinct interfaces between the HDCP controller and DP TX controller. The AUX interface is used for authentication and key exchange during link initialization. The DP TX acts as an intermediary between the HDCP controller and the external receiver/repeater. The AES stream interface is used to send the session key information to the DP TX, which it uses to encrypt the video data before sending it out. HDCP has SST mode (single AES stream) or MST (dual AES stream).
DP TX Output
Depending on the video resolution and number of lanes (x1, x2, or x4) chosen, the video output is sent out on this interface to the PCS of the USB/DP ComboPHY.