AT83SND1CXXX-ROTIL datasheet(108/212 Pages) ATMEL

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108

4109J–8051–10/06

AT8xC51SND1C

15. MultiMedia Card Controller

The AT8xC51SND1C implements a MultiMedia Card (MMC) controller. The MMC is used to

store MP3 encoded audio files in removable Flash memory cards that can be easily plugged or

removed from the application.

15.1

Card Concept

The basic MultiMedia Card concept is based on transferring data via a minimum number of

signals.

15.1.1

Card Signals

The communication signals are:

•

CLK: with each cycle of this signal a one bit transfer on the command and data lines is done.

The frequency may vary from zero to the maximum clock frequency.

•

CMD: is a bi-directional command channel used for card initialization and data transfer

commands. The CMD signal has 2 operation modes: open-drain for initialization mode and

push-pull for fast command transfer. Commands are sent from the MultiMedia Card bus

master to the card and responses from the cards to the host.

•

DAT: is a bi-directional data channel. The DAT signal operates in push-pull mode. Only one

card or the host is driving this signal at a time.

15.1.2

Card Registers

Within the card interface five registers are defined: OCR, CID, CSD, RCA and DSR. These can

be accessed only by the corresponding commands.

The 32-bit Operation Conditions Register (OCR) stores the VDD voltage profile of the card. The

The 128-bit wide CID register carries the card identification information (Card ID) used during

the card identification procedure.

The 128-bit wide Card-Specific Data register (CSD) provides information on how to access the

card contents. The CSD defines the data format, error correction type, maximum data access

time, data transfer speed, and whether the DSR register can be used.

The 16-bit Relative Card Address register (RCA) carries the card address assigned by the host

during the card identification. This address is used for the addressed host-card communication

after the card identification procedure.

The 16-bit Driver Stage Register (DSR) can be optionally used to improve the bus performance

for extended operating conditions (depending on parameters like bus length, transfer rate or

number of cards).

15.2

Bus Concept

The MultiMedia Card bus is designed to connect either solid-state mass-storage memory or I/O-

devices in a card format to multimedia applications. The bus implementation allows the cover-

age of application fields from low-cost systems to systems with a fast data transfer rate. It is a

single master bus with a variable number of slaves. The MultiMedia Card bus master is the bus

controller and each slave is either a single mass storage card (with possibly different technolo-

gies such as ROM, OTP, Flash etc.) or an I/O-card with its own controlling unit (on card) to

perform the data transfer.

The MultiMedia Card bus also includes power connections to supply the cards.

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