MMC/SD Host Controller
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7.12 MMC/SD Host Controller
The MMC/SD host controller provides an interface between the TI925T and
either MMC or SD memory card plus up to three serial flash cards and handles
MMC/SD or SPI transactions with minimal TI925T intervention. All references
to a local host in this section refer to the TI925T MPU processor.
The following combination of external devices is supported:
-
One or more MMC memory cards sharing the same bus plus up to three
devices with 8-bit SPI protocol interface (flash serial memory).
-
One single-SD memory card plus up to three devices with 8-bit SPI proto-
col interface.
Other combinations like two SD cards, one MMC card + one SD card are not
supported.
The application interface is responsible for managing transaction semantics.
The MMC/SD host controller handles MMC/SD protocol at transmission level,
packing data, adding cyclic redundancy check (CRC), start/end bit, and check-
ing for syntactical correctness. SD mode wide bus width is also supported.
The application interface can send every MMC/SD command and either poll
for the status of the adapter or wait for an interrupt request, which is sent back
in case of exceptions or to warn for end of operations. The application interface
can read card responses or flag registers. It can also mask individually inter-
rupt sources. All these operations can be performed by reading and writing
control registers.