SNLA356 September   2020 DS90UB941AS-Q1 , DS90UH941AS-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2MIPI DSI Source Requirements
    1. 2.1 Supported DSI Modes
    2. 2.2 Clocking Rates and Clock Type
    3. 2.3 Blanking or Low Power Modes (BLLP)
    4. 2.4 DSI Packet Timing
      1. 2.4.1 Non-Burst Mode With Sync Pulses
      2. 2.4.2 Non-Burst Mode With Sync Events
      3. 2.4.3 Burst Mode
  5. 3Bring-Up and Debug Flow
  6. 4Example Bringup Scenarios
    1. 4.1 Discontinuous Clock
    2. 4.2 Missing Periodic Low Power Transitions
    3. 4.3 Incorrect DSI Packet Timing
    4. 4.4 THS-SKIP Configuration
    5. 4.5 End of Transmission Packets (EoTp)
    6. 4.6 Configuration of Sync Width for Event Mode/Burst Mode
  7. 5Summary
  8. 6References

2.1 Supported DSI Modes

Before attempting to link a DSI source with DS90UB941AS-Q1, it is important to understand the supported MIPI DSI modes for the serializer. DS90UB941AS-Q1 supports MIPI DSI video mode only. It does not support MIPI DSI command mode for low speed communications with displays that use integrated video memory. The serializer supports four different RGB video formats:

  • RGB888 (Packed Pixel Stream, 24-bit Format, Data Type 0x3E)
  • RGB666 (Loosely Packed Pixel Stream, 18-bit format in Three Bytes, Data Type 0x2E)
  • RGB666 (Packed Pixel Stream, 18-bit Format, Data Type 0x1E)
  • RGB565 (Packed Pixel Stream, 16-bit Format, Data Type 0x0E)

The RGB video formats are automatically converted, if necessary, to 3-byte RGB888 for transmission over FPD-Link III. The DSI_BYTES_PER_PIXEL bits in DS90UB941AS-Q1 register 0x54 should be configured to match the expected pixel packing for the DSI port prior to enabling the DSI receiver. The default setting is 3 bytes-per-pixel which matches the RGB888 video format.

The DS90UB941AS-Q1 also supports pass-through of four DSI YCbCr video formats:

  • Packed Pixel Stream, 12-bit YCbCr 4:2:0 Format, Data Type 0x3D
  • Packed Pixel Stream, 16-bit YCbCr 4:2:2 Format, Data Type 0x2C
  • Packed Pixel Stream, 24-bit YCbCr 4:2:2 Format, Data Type 0x1C
  • Loosely Packed Pixel Stream, 20-bit YCbCr 4:2:2 Format, Data Type 0x0C

Each of these formats is aligned to the 3-bytes-per-pixel forward channel but is not converted to RGB888.

Most common display applications utilize RGB888 video format for 24 bits per pixel. It is important to note the expected video data type hex code based on the source configuration before progressing with the system bring-up. This will be useful to know as the received packet data type for the MIPI DSI input can be reported by the status registers of DS90UB941AS-Q1 in real time. If there are unexpected issues with the video output colors or there is no video at the display, this provides a quick way to check if the video format from the source is properly recognized by the DS90UB941AS-Q1 receiver.

DS90UB941AS-Q1 supports all three video mode operating configurations:

  • Non-burst mode with sync pulses
  • Non-burst mode with sync events
  • Burst mode