
REF: BB_SRM_xM BeagleBoard-xM System
Reference Manual
Revision A2
Page 84 of 164
8.15.3 Card Detect
When a card is inserted into the connector, the Card Detect pin is grounded. This is
detected on pin P12 of the TPS65950. An interrupt, if enabled, is sent to the processor
via the interrupt pin. The SW can be written such that the system comes out of sleep or a
reduced frequency mode when the card is detected.
8.15.4 Booting From SD/MMC Cards
The ROM code supports booting from the microSD cards with some limitations:
o Support for SD cards compliant with the Multimedia Card System Specification
v4.2 from the MMCA Technical Committee and the Secure Digital I/O Card
Specification v2.0 from the SD Association. Including high-capacity (size >2GB)
cards: HC-SD and HC MMC.
o 3-V power supply, 3-V I/O voltage on port 1
o Initial 1-bit MMC mode, 4-bit SD mode.
o Clock frequency:
– Identification mode: 400 kHz
– Data transfer mode: 20 MHz
o Only one card connected to the bus
o FAT12/16/32 support, with or without master boot sector (MBR).
The high-speed microSD host controllers handle the physical layer while the ROM code
handles the simplified logical protocol layer (read-only protocol). A limited range of
commands is implemented in the ROM code. The MMC/SD specification defines two
operating voltages for standard or high-speed cards. The ROM code only supports
standard operating voltage range (3-V). The ROM code reads out a booting file from the
card file system and boots from it.
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