There are two SD/eMMC controllers on the Versal ACAP. The SD/eMMC controllers can be used for SD or eMMC and are mutually exclusive. When the controller is selected to support eMMC the SD mode cannot be used. Only one of the SD/eMMC controllers supports the eMMC boot mode, the SD1/eMMC1 controller.
The SD1/eMMC1 controller supports the 4.51 eMMC specification. FAT 16/32 file systems and select raw partition combinations are supported for reading the boot images from eMMC for primary boot. Raw partitions, not formatted and without a file system, are supported for primary boot mode, the boot partition 1, boot partition 2, or the user area of the eMMC. Using eMMC FAT 16/32 file system for primary boot mode and eMMC as secondary boot mode is not supported. The image search limit for eMMC1 boot mode is listed in Table 3. See the Versal ACAP System Software Developers Guide (UG1304) for additional details on supported raw boot options.
In the eMMC1 boot mode, the RCU BootROM runs at an eMMC1 device clock frequency between 8.7 MHz and 19.3 MHz dependent on the REF_CLK setting. The eMMC1 boot mode supports 1.8V and 1-bit, 4-bit, and 8-bit data interfaces. The BootROM uses auto-width detection to determine the data bus width for initial boot. The auto-bus width detection starts by checking the 8-bit data bus width, followed by 4-bit data bus width, and then 1-bit data bus width.