SPRUJ28E November 2021 – September 2024 AM68 , AM68A , TDA4AL-Q1 , TDA4VE-Q1 , TDA4VL-Q1
The sequence for controlling the SD Bus Power is described in Figure 12-117.
(1) By reading the MMCSD0_CAPABILITIES register, get the support voltage of the Host Controller.
(2) Set MMCSD0_POWER_CONTROL[3-1] SD_BUS_VOLTAGE bit field with maximum voltage that the Host Controller supports.
(3) Set MMCSD0_POWER_CONTROL[0] SD_BUS_POWER bit to 1.
(4) Get the OCR value of all function internal of SD card.
(5) Judge whether SD Bus voltage needs to be changed or not. In case where SD Bus voltage needs to be changed, go to step (6). In case where SD Bus voltage does not need to be changed, go to "End".
(6) Set MMCSD0_POWER_CONTROL[0] SD_BUS_POWER bit to 0 for clearing this bit. The card requires voltage rising from 0 volt to detect it correctly. The Host Driver shall clear MMCSD0_POWER_CONTROL[0] SD_BUS_POWER bit before changing voltage by setting MMCSD0_POWER_CONTROL[3-1] SD_BUS_VOLTAGE bit field.
(7) Set MMCSD0_POWER_CONTROL[3-1] SD_BUS_VOLTAGE bit field.
(8) Set MMCSD0_POWER_CONTROL[0] SD_BUS_POWER to 1.
Note: Step (2) and step (3) can be executed at same time. And also, step (7) and step (8) can be executed at same time.