Freescale Semiconductor

Application Note

Document Number: AN3049

Rev. 0, 10/2005

1Abstract

This document describes the Multimedia Card (MMC)

and the Secure Digital (SD) modules on Freescale

Semiconductor’s i.MX application processors. This

document gives an overview of the similarities and

differences of both the MMC and SD protocols and

cards including configuration of the MMC/SD module.

The document also describes the interface of the

MMC/SD modules, specifically the card identification

mode and the system clock controller, along with

example code. System considerations at various data

transfer rates are included.

This document applies to the following devices,

collectively called i.MX throughout:

• MC9328MX1

• MC9328MXL

• MC9328MX21

Setup and Use of the Multimedia

Card/Secure Digital Host Controller

MC9328MX1, MC9328MXL, and MC9328MX21

by: Jason Castillo

Contents

1 Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1

2 MMC/SD Module Overview . . . . . . . . . . . . . . . . .2

3 MMC/SD Module Configuration . . . . . . . . . . . . . .2

4 Interfacing with the MMC/SD Module . . . . . . . . .5

5 Special Considerations . . . . . . . . . . . . . . . . . . .10

6 References . . . . . . . . . . . . . . . . . . . . . . . . . . . . .11

MMC/SD Module Overview

Setup and Use of the Multimedia Card/Secure Digital Host Controller Application Note, Rev. 0

2 Freescale Semiconductor

2 MMC/SD Module Overview

This section provides an overview of both the Multimedia Card (MMC) and Secure Digital Card (SD)

modules. The MMC/SD module includes the following features:

• Supports up to 10 cards (including one SD card)

• Password protection for cards

• Built-in programmable frequency counter for MMC/SD bus

• Maskable hardware interrupt for card detection (insertion/removal), SD I/O interrupt, internal

status, and FIFO status

• Contains an integrated 32 × 16-bit FIFO

• Supports plug-and-play (Pop)

• Supports many SD functions including multiple I/O and combined I/O and memory

• Supports up to seven I/O functions plus one memory on a single SD I/O card

• Card can interrupt MMC/SD module

• Support single or multiple block access, or stream access to the card for read, write, or erase

operations

• Supports SD I/O ReadWait and interrupt detection during 1- or 4-bit access

2.1 Multimedia Card (MMC) Protocol

The MMC is low cost data storage and communication medium implemented as a hardware card with a

simple control unit and a compact, easy-to-implement interface that is designed to cover a wide variety of

applications. It is based on an advanced 7-pin serial bus designed to operate over a voltage range of 2.0 to

3.6 V. Note that the maximum operating voltage range for the i.MX is 3.3 V. Therefore the i.MX-based

design is limited to a supply range of 2.0 to 3.3 V.

2.2 Secure Digital Card (SD) Protocol

The SD is an extended version of the MMC with two additional pins. The additional pins are designed to

meet the security, capacity, performance, and environmental requirements inherent in new audio and

video consumer electronic devices. The physical form factor and data transfer protocol are compatible

with the MMC. The SD is composed of a memory card and an I/O card.

3 MMC/SD Module Configuration

The MMC card has 7 pins and the SD card has 9 pins. The pins are used to communicate with other

functions within the card. The pin assignment and form factor are shown in Table 1.