SPRUI30H November 2015 – May 2024 DRA745 , DRA746 , DRA750 , DRA756
If the eMMC Alternate Boot operation fails in time-out, or the requested boot device is an SD card, the ROM code initializes the memory device or card connected on the eMMC and SD card interface using 1.8 V for eMMC and standard high-voltage range (3.0 V) for SD card I/Os. If neither a card nor memory device is detected, the ROM code moves to the next booting device. The standard identification process and relative card address (RCA) assignment are performed. The ROM code assumes that only one memory or card is connected on the bus. This is done using the CMD line common to the SD and eMMC memory devices. The eMMC and SD standards describe this phase as the initialization phase. They differ in the commands involved, as described in Figure 32-25. The ROM code uses CMD55 to discriminate between eMMC and SD cards; that is, CMD55 is only supported by the SD standard. Depending on response received or not, ACMD41 (the combination of CMD55 and CMD41 for SD) or CMD1 (for MMC) is sent. If no response is received this time, no devices are connected and the ROM code exits eMMC/SD booting with FAIL.
Figure 32-24 shows the eMMC/SD detection procedure.
Figure 32-25 shows the eMMC/SD detection procedure.
Figure 32-26 shows the eMMC/SD detection procedure.