The SD PS controller supports auto-tuning for SDR-104,SDR-50 and HS200. Whereas, manual tuning is supported for HSD/SDR25/DDR50 modes and eMMC high-speed SDR/DDR modes in order to find the valid rx clock delay. The tuning unit generates the delay controls to the external delay controller. The tuning unit receives the 64-byte tuning word (SD mode) or 128-byte tuning word (eMMC mode) and maintains a tuning vector to determine the optimal delay. The tuning unit can be configured with the number of supported delay taps (180 maximum). Using this, the tuning unit performs tuning and selects the optimal tap point for the receive clock.
Note: Programming the delay taps non-sequentially might lead to the failing of the auto-tuning. See Answer Record 65676 for the work-around sequence.