User Manual

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5.3.5 Boot Modes
As mentioned earlier, there are four boot modes:
• eMMC Boot… This is the default boot mode and will allow for the fastest boot
time and will enable the board to boot out of the box using the pre-flashed
OS image without having to purchase an microSD card or an microSD card
writer.
• SD Boot… This mode will boot from the microSD slot. This mode can be used to
override what is on the eMMC device and can be used to program the eMMC
when used in the manufacturing process or for field updates.
• Serial Boot… This mode will use the serial port to allow downloading of the
software direct. A separate USB to serial cable is required to use this port.
•
USB Boot… This mode supports booting over the USB port.
Software to support USB and serial boot modes is not provided by beagleboard.org.
Please contact TI for support of this feature.
A switch is provided to allow switching between the modes.
• Holding the boot switch down during a removal and reapplication of power
without a microSD card inserted will force the boot source to be the USB port and
if nothing is detected on the USB client port, it will go to the serial port for
download.
• Without holding the switch, the board will boot try to boot from the eMMC. If it is
empty, then it will try booting from the microSD slot, followed by the serial
port, and then the USB port.
• If you hold the boot switch down during the removal and reapplication of
power to the board, and you have a microSD card inserted with a bootable
image, the board will boot from the microSD card.
NOTE: Pressing the RESET button on the board will NOT result in a change of the
boot mode. You MUST remove power and reapply power to change the boot mode.
The boot pins are sampled during power on reset from the PMIC to the processor.
The reset button on the board is a warm reset only and will not force a boot mode
change.
5.4 Power Management
The TPS65217C power management device is used along with a separate LDO to
provide power to the system. The TPS65217C version provides for the proper voltages
required for the DDR3L. This is the same device as used on the original BeagleBone with
the exception of the power rail configuration settings which will be changed in the
internal EEPROM to the TPS65217C to support the new voltages.