Boot Mode; Boot Modes - Enclustra Mercury SA1 SoC Module User Manual

HPS and FPGA Configuration Pins
The BSEL and CSEL pins determine in which memory interface is the boot loader stored and how to clock
the interface; details on BSEL and CSEL pins when using the HPS boot are available in the Booting and
Configuration Introduction document [20]. The MSEL pins, which are used to select an FPGA configuration
scheme, are described in the Cyclone V Device Handbook [19].
3.2

Boot Mode

The BOOT_MODE signals determine whether the SoC device boots from the QSPI flash or from an SD card
connected to the SD pins on the HPS bank.
Starting with revision 3, booting from eMMC flash is supported. The eMMC flash clock is interrupted when
the eMMC flash enable signal, EMMC_EN#, is inactive (for example, when booting from SD card). When
booting from the QSPI flash, it is possible to access either the SD card or the eMMC flash, depending on
the EMMC_EN# signal.
EMMC_EN# signal is driven by the boot mode signals. This signal is also mapped to HPS pin 53 and can be
toggled to switch between eMMC and SD card interfaces, provided that the SDIO devices are not used at
the moment of switching (for example for the filesystem).
Figure 11: Boot Modes - eMMC Flash available starting with Revision 3
Table 31 describes the available boot modes and the corresponding boot mode signals.
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