BeagleBone BBONEBLK_SRM, Справочное руководство

Страница: 53 / 108

REF: BBONEBLK_SRM
BeagleBone Black System
Reference Manual
Rev A5.2
Page 53 of 108
6.4 2GB eMMC Memory
The eMMC is a communication and mass data storage device that includes a Multi-
MediaCard (MMC) interface, a NAND Flash component, and a controller on an
advanced 11-signal bus, which is compliant with the MMC system specification. The
nonvolatile eMMC draws no power to maintain stored data, delivers high performance
across a wide range of operating temperatures, and resists shock and vibration disruption.
One of the issues faced with SD cards is that across the different brands and even within
the same brand, performance can vary. Cards use different controllers and different
memories, all of which can have bad locations that the controller handles. But the
controllers may be optimized for reads or writes. You never know what you will be
getting. This can lead to varying rates of performance. The eMMC card is a known
controller and when coupled with the 8bit mode, 8 bits of data instead of 4, you get
double the performance which should result in quicker boot times.
The following sections describe the design and device that is used on the board to
implement this interface.
6.4.1 eMMC Device
The device used in a Micron
MTFC2GMTEA-0F_WT 2GB eMMC device. This is a
new device and so for documentation and support, you will need to contact your local
Micron representative.
The package is a 153 ball WFBGA device. The footprint on the BeagleBone Black for
this device supports 4GB and 8GB devices. As this is a JEDEC standard, there are other
suppliers that may work in this design as well. The only device that has been tested is the
MTFC2GMTEA-0F_WT .