Intel PXA255 manual MultiMediaCard Controller

Models: PXA255

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MultiMediaCard Controller

15

15.1Overview

The PXA255 processor MultiMediaCard (MMC) controller acts as a link between the software used to access the processor and the MMC stack (a set of memory cards). The MMC controller is designed to support the MMC system, a low-cost data storage and communications system. A detailed description of the MMC system is available through the MMC Association’s web site at www.mmca.org. The processor’s MMC controller is based on the standards outlined in The MultiMediaCard System Specification Version 2.1 with the exception that one- and three-byte data transfers are not supported and the maximum block length is 1023.

The MMC controller supports the translation protocol from a standard MMC or Serial Peripheral Interface (SPI) bus to the MMC stack. The software used to access the processor must indicate whether to use MMC or SPI mode as the protocol to communicate with the MMC controller.

The MMC controller features:

Data transfer rates up to 20 Mbps

A response FIFO

Dual receive data FIFOs

Dual transmit FIFOs

Support for two MMCs in either MMC or SPI mode

The MMC controller contains all card-specific functions, serves as the bus master for the MMC system, and implements the standard interface to the card stack. The controller handles card initialization; CRC generation and validation; and command, response, and data transactions.

The MMC controller is a slave to the software and consists of command and control registers, a response FIFO, and data FIFOs. The software has access to these registers and FIFOs and generates commands, interprets responses, and controls subsequent actions.

Figure 15-1shows a block diagram of the interaction of a typical MMC stack, the MMC controller, and a software.

Figure 15-1. MMC System Interaction

Software

Interface

 

MMCLK

 

Processor’s

MMCMD

 

MMDAT

MMC

MMC

MMCCS0

Stack

Controller

 

 

MMCCS1

 

MMCCS0 and MMCCS1 are only used in SPI mode.

Intel® PXA255 Processor Developer’s Manual

15-1

Page 505
Image 505
Intel PXA255 manual MultiMediaCard Controller