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

2.3 Blanking or Low Power Modes (BLLP)

The Blanking or Low Power period (BLLP) period is defined as a time during which video or video synchronization packets are not transmitted. During the BLLP period, the DSI source may enter Idle Mode (LP-11), stay in HS mode (LP-00) and transmit HS blanking packets, or transmit non-video packets to the DSI receiver. Typically the DSI source configuration will allow flexibility in configuring BLLP behavior during the various video blanking intervals.

According to the MIPI DSI v1.3.1 standard section 8.11.1, a DSI source should periodically end HS transmission and drive the data lanes to the LP-11 state at least once per frame to enable PHY synchronization. Correspondingly, DS90UB941AS-Q1 uses this LP to HS transition as a signal to initialize its DSI receiver after power up. (Note this only applies to the data lanes and not the clock). Some common DSI source drivers do not follow the MIPI DSI standard closely with regards to this requirement and will remain in HS (LP-00) mode during all BLLP periods. This poses a common pitfall for system bring-up, as the DS90UB941AS-Q1 cannot initialize if it does not see any LP to HS transitions on the data lanes. It is important to ensure that the DSI source follows the MIPI DSI standard closely, and enables LP-11 during at least one of the BLLP periods of the video frame.