SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The start-up sequence described in Figure 6-61 assumes that the rest of the chip is ready (all clocks are present except tx_byte_hs_clk, application it is ready...) and that the DSI is ready (reset de-asserted).
The following is the most common start up sequence:
Firstly, application layer programs and enables the PLL, then waits for a period for the PLL to lock (minimum time will be defined by the PHY documentation). At the end of the minimum wait period, the application layer should poll the PLL lock status register periodically to confirm lock status, repeating until confirmed. At the end of this step, it is assumed that a clock is present on the tx_byte_hs_clk input (this step may be replaced by an interrupt-based alternative if available from the selected DPHY or provided in the system integration logic).
During the time taken by the PLL to lock, the application can program the configuration registers and prepare the DSI link. This can also be done after the PLL is locked. It should at least configure enough to be able to use LP mode to send direct commands.
Enable clock and data lane(s) per the needs. This action is only concerned with programming registers that control the D-PHY lane enable signal. The active lane configuration with the DSI_MCTL_MAIN_PHY_CTL and DSI_MCTL_MAIN_EN registers must be programmed to match, i.e. for two data lanes (0 and1).
Start the lane in the DCB. The DCB state machine puts the lanes in the correct state to be ready.
At this step, the DSI link should be able to access to display - at least in LP mode. If the system (DSI link and display) is fully programmed, code to display image can be started. If display characteristics must be read from the display and the system is programmed in LP mode, this is time to read the displays parameters to allow correct programming of the DSI. A new round of programming can then take place to set-up the system, based on the parameters which have been read fro the display.
The DSI internal setting is now completed and it is ready to accept data. The application can now enable the interface so that the stall signal is removed and that DSI link can accept data.
When the procedure described above is terminated, it does not imply that display itself is ready. At this stage, the D-PHY and DSI link are ready to send/receive data to/from display and thus application may still need to initialize the display itself.