Hard Processor System Technical Reference Manual: Agilex™ 5 SoCs
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5.4.9.1. SD Card Level Shifting
HPS I/O only supports 1.8 V signaling. Most SD cards require 3.3 V operation at initial power-up time, and they typically require switching to 1.8 V after initialization time to support higher speed operation.
To support 3.3 V operation, a level shifter is required. Level shifters are available on the market, designed specifically for this purpose.
There are also LVS SD cards that only support 1.8 V operation, and the controller could communicate with those cards without the need of level shifters. To properly detect and initialize LVS SD cards, you need to use the PU_PD_DAT2 signal to control the pull up or down of the DAT2 signal.
Refer to the SD Voltage Switching section for more details.