Information Technology Reference
In-Depth Information
4
Accessing
Flash Memory Cards
For many embedded systems, a good choice for storage is a a MultiMedi-
aCard accessed via SPI. This chapter shows what's involved in implementing
SPI communications with MultiMediaCards. SD-Card hosts can use the
same interface and firmware.
The Interface
The Serial Peripheral Interface (SPI) originated at Motorola (now Freescale
Semiconductor). Many microcontrollers from Motorola/Freescale and oth-
ers have hardware support for SPI. In systems without hardware support,
the communications can be controlled entirely in firmware.
Every SPI communication is between a host, or master, and a MultiMedi-
aCard or other slave device. The host controls the interface's clock and
chip-select lines.
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