Intel PXA250 and PXA210 manual MultiMediaCard MMC, Schematics, Signal Description

MultiMediaCard (MMC) 5

The MultiMediaCard (MMC) is a low cost data storage and communication media. The MMC supports the translation protocol from a standard MMC or Serial Peripheral Interface (SPI) bus to an application bus.

The MMC controller in the applications processor is compliant with The MultiMediaCard System Specification, Version 2.1. The only exception is one and three byte data transfers are not supported. The MMC controller is capable of communicating with a card in MMC or SPI mode. Your application is responsible for specifying the MMC controller communication mode.

5.1Schematics

The MultiMediaCard (MMC) controller on the applications processor supports MMC and SDCard devices. (The MMC controller does not support SDCard nibble mode.) This section presents several options on how to connect each type of device to the controller.

5.1.1Signal Description

MMC controller signal functions are described in Table 5-1.

Table 5-1. MMC Signal Description

Signal Name	Input/Output	Description
MMCLK	Output	Clock signal to MMC
MMCMD	BiDirectional	Command line
MMDAT	BiDirectional	Data line
MMCCS0	Output	Chip Select 0
MMCCS1	Output	Chip Select 1

The MMCLK, MMCCS0, and MMCCS1 signals are routed through alternate functions within the applications processor general purpose input/output (GPIO) module. Each of these signals can be programmed to a particular GPIO pin.

The signals defined in The MultiMediaCard System Specification for an MMC device are CLK, CMD, and DAT which correspond to the MMCLK, MMCMD, and MMDAT in the applications processor, respectively. The two chip selects in the controller are for the MMC SPI mode and correspond to the reserved pin of two different devices, defined in the specification.

The signals defined in the Physical Layer Specification of the SD Memory Card Specifications for an SDCard device are CLK, CMD, and DAT0-DAT3. The obvious difference is the number of DAT signals. In addition, the socket for an SDCard contains mechanical switches for write protect (WP) and card detect (CD). For an SDCard to be connected to the MMC controller, only one data line, DAT0, is used. Otherwise the signal mapping remains the same as an MMC device. The WP and CD switches on the socket are discussed in Section 5.1.2, “How to Wire” on page 5-2.

PXA250 and PXA210 Applications Processors Design Guide 5-1