SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
Triggers are one of the groups of direct commands that can be sent and received using the DPHY in Low Power escape mode. The trigger_val[3:0] bits (in the registers DIRECT_CMD_MAIN_SETTINGS and DIRECT_CMD_STS) are used to define which of the four possible trigger entry codes has to be sent or has been received. The register fields described above are copied in signal ppi_d1_tx_trigger_esc[3:0] (for trigger_val[3:0] of DIRECT_CMD_MAIN_SETTINGS) or are a copy of ppi_d1_rx_trigger_esc[3:0] (for trigger_val[3:0] of DIRECT_CMD_STS). Only one bit out of the four should be set else the D-PHY behavior is not very precisely defined. Table 12-363 gives the trigger mapping in the system.
Trigger name | Trigger entry code | trigger_val | meaning in TX direction | meaning in RX direction |
---|---|---|---|---|
trigger 0 - reset | 01100010 | 1b0001 | Reset | Not affected by DSI spec |
trigger 1 - unknown 3 | 01011101 | 1b0010 | Not affected by DSI spec | TE response(1) |
trigger 2- unknown 4 | 00100001 | 1b0100 | Not affected by DSI spec | Acknowledge with no error(1) |
trigger 3 - unknown 5 | 10100000 | 1b1000 | Not affected by DSI spec | Not affected by DSI spec |
Trigger Reset – This will request from the display and expects an immediate reset of the DSI command/video mode with all pending requests in TX sending path FIFO for transfer to be discarded.
Acknowledge – This is a response to DSITX controller. The host processor may request a command acknowledge and error information related to any transmission by asserting Bus Turnaround with the transmission. The peripheral shall respond with ACK Trigger Message if there are no errors and with Acknowledge and Error Report packet if any errors were detected in previous transmissions. Appropriate flags shall be set to indicate what errors were detected on the preceding transmissions.
If the transmission was a Read request, the peripheral shall return READ data without issuing additional ACK Trigger Message or an Acknowledge and Error Report packet if no errors were detected. If there was an error in the Read request, the peripheral shall return the appropriate Acknowledge and Error Report unless the error was a single-bit correctable error. In that case, the peripheral shall return the requested READ data packet followed by Acknowledge and Error Report packet with appropriate error bits set.
Tearing Effect - The Tearing effect on the display is avoided by having synchronization information from the display. It is used only in command mode. Users are responsible for selecting the command mode for the VC using the TE feature and selecting the polling or automatic mechanism.
The user is responsible for ensuring that there is a delay after a trigger is issued by the host to the panel, before any other action, message or trigger is performed. When the host issues a reset trigger, the system will expect the controller to stop and re initialise the clock and data links. All other triggers issued by the host will be application specific and are outside the scope of this document.