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

4.5 End of Transmission Packets (EoTp)

DSI devices compliant to the MIPI DSI v1.0 specification and later are required to generate End of Transmission Packets (EoTp) following any HS data transmission. The main objective of the EoTp is to enhance the robustness of the DSI interface during transition from HS to LP mode so that the receiver can clearly detect the end of HS transmission even in the presence of non-optimal signaling conditions. To support backwards compatibility and interop between DSI peripherals, the standard mandates that the transmitter and receiver devices should have optional capability to utilize or not utilize EoTp functionality. DS90UB941AS-Q1 expects the DSI source to send EoTp by default since it is a DSI v1.3.1 compliant receiver, so if the source does not generate EoTp, then DS90UB941AS-Q1 will report an error condition.

Symptoms:

  • DS90UB941AS-Q1 reports DSI_EOT_ERR in the DSI_STATUS register

How to Verify:

  1. Check the DSI_EOT_ERR flag via I2C:
    1. Write 0x40 = 0x04 for DSI Port 0 or 0x40 = 0x08 for DSI Port 1
    2. Write 0x41 = 28
    3. Read 0x42 and check for bit 2, which indicates DSI_EOT_ERR when bit 2 = 1. This flag is cleared on read.

Resolution:

It is recommended to enable EoTp generation from the source device if possible. This should be a configurable option in the DSI source kernel driver. If the source does not support EoTp generation, then enable DSI_NO_EOTPKT = 1 in the DSI_CONFIG_1 register which will mask EoTp errors in the DSI_STATUS register.

Typically, this error condition does not cause any visual impact to the display, but it may affect the DS90UB941AS-Q1's capability to detect a true EoT error in a system which does not utilize EoTp.