BeagleBone Black System
Reference Manual
Page 31 of 108
connector will support larger capacity SD cards. The SD card is not provided with the
board. Booting from MMC0 will be used to flash the eMMC in the production
environment or can be used by the user to update the SW as needed.
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 SD card or an SD card writer.
SD Boot…This mode will boot from the uSD 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 boot without a SD 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 from eMMC. If it is empty,
then it will try booting from the uSD slot, followed by the serial port, and then
the USB port.
If you hold the boot switch down during boot, and you have a uSD card
inserted with a bootable image, the board will boot form the uSD card.
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 TPS65217 to support the new voltages.
DDR3L requires 1.5V instead of 1.8V on the DDR2 as is the case on the original
BeagleBone. The 1.8V regulator setting has been changed to 1.5V for the DDR3L. The
LDO3 3.3V rail has been changed to 1.8V to support those rails on the processor. LDO4
is still 3.3V for the 3.3V rails on the processor. An external LDOTLV70233 provides the
3.3V rail for the rest of the board.
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