Datasheet

SAM9261 [DATASHEET]
Atmel-6062O-ATARM-SAM9261-Datasheet_21-Jun-16
560
34.9 SD Card Operations
The MultiMedia Card Interface allows processing of SD Memory (Secure Digital Memory Card) Card commands.
SD cards are based on the Multi Media Card (MMC) format, but are physically slightly thicker and feature higher
data transfer rates, a lock switch on the side to prevent accidental overwriting and security features. The physical
form factor, pin assignment and data transfer protocol are forward-compatible with the MultiMedia Card with some
additions.SD is covered by numerous patents and trademarks, and licensing is only available through the Secure
Digital Card Association.
The SD Card communication is based on a 9-pin interface (Clock, Command, 4 x Data and 3 x Power lines). The
communication protocol is defined as a part of this specification. The main difference between the SD Card and
the MultiMedia Card is the initialization process.
The SD Card Register (MCI_SDCR) allows selection of the Card Slot and the data bus width.
The SD Card bus allows dynamic configuration of the number of data lines. After power up, by default, the SD
Card uses only DAT0 for data transfer. After initialization, the host can change the bus width (number of active
data lines).