Texas Instruments TMS320DM644x User manual

TMS320DM644x DMSoC

Multimedia Card (MMC)/Secure Digital (SD)

Card Controller

User's Guide

Literature Number: SPRUE30B

September 2006

2 SPRUE30B – September 2006

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Contents

Preface ............................................................................................................................... 7

1 Introduction ................................................................................................................ 9

1.1 Purpose of the Peripheral ....................................................................................... 9

1.2 Features ........................................................................................................... 9

1.3 Functional Block Diagram ....................................................................................... 9

1.4 Supported Use Case Statement .............................................................................. 10

1.5 Industry Standard(s) Compliance Statement ............................................................... 10

2 Peripheral Architecture .............................................................................................. 10

2.1 Clock Control .................................................................................................... 12

2.2 Signal Descriptions ............................................................................................. 13

2.3 Protocol Descriptions........................................................................................... 13

2.4 Data Flow in the Input/Output FIFO .......................................................................... 15

2.5 Data Flow in the Data Registers (MMCDRR and MMCDXR) ............................................. 17

2.6 FIFO Operation During Card Read Operation .............................................................. 19

2.7 FIFO Operation During Card Write Operation .............................................................. 21

2.8 Reset Considerations .......................................................................................... 23

2.9 Initialization ...................................................................................................... 23

2.10 Interrupt Support ................................................................................................ 27

2.11 DMA Event Support ............................................................................................ 28

2.12 Power Management ............................................................................................ 28

2.13 Emulation Considerations ..................................................................................... 28

3 Procedures for Common Operations ........................................................................... 29

3.1 Card Identification Operation .................................................................................. 29

3.2 MMC/SD Mode Single-Block Write Operation Using CPU ................................................ 32

3.3 MMC/SD Mode Single-Block Write Operation Using the EDMA ......................................... 34

3.4 MMC/SD Mode Single-Block Read Operation Using the CPU ........................................... 34

3.5 MMC/SD Mode Single-Block Read Operation Using EDMA .............................................. 35

3.6 MMC/SD Mode Multiple-Block Write Operation Using CPU .............................................. 36

3.7 MMC/SD Mode Multiple-Block Write Operation Using EDMA ............................................ 38

3.8 MMC/SD Mode Multiple-Block Read Operation Using CPU .............................................. 38

3.9 MMC/SD Mode Multiple-Block Read Operation Using EDMA ............................................ 39

4 Registers .................................................................................................................. 40

4.1 MMC Control Register (MMCCTL) ........................................................................... 41

4.2 MMC Memory Clock Control Register (MMCCLK) ......................................................... 42

4.3 MMC Status Register 0 (MMCST0) .......................................................................... 43

4.4 MMC Status Register 1 (MMCST1) .......................................................................... 45

4.5 MMC Interrupt Mask Register (MMCIM) ..................................................................... 46

4.6 MMC Response Time-Out Register (MMCTOR) ........................................................... 47

4.7 MMC Data Read Time-Out Register (MMCTOD) .......................................................... 48

4.8 MMC Block Length Register (MMCBLEN) .................................................................. 49

4.9 MMC Number of Blocks Register (MMCNBLK) ............................................................ 50

4.10 MMC Number of Blocks Counter Register (MMCNBLC) .................................................. 50

4.11 MMC Data Receive Register (MMCDRR) ................................................................... 51

4.12 MMC Data Transmit Register (MMCDXR) .................................................................. 51

SPRUE30B – September 2006 Table of Contents 3

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4.13 MMC Command Register (MMCCMD) ...................................................................... 52

4.14 MMC Argument Register (MMCARGHL) .................................................................... 54

4.15 MMC Response Registers (MMCRSP0-MMCRSP7) ...................................................... 55

4.16 MMC Data Response Register (MMCDRSP) ............................................................... 57

4.17 MMC Command Index Register (MMCCIDX) ............................................................... 57

4.18 MMC FIFO Control Register (MMCFIFOCTL) .............................................................. 58

Appendix A Revision History ............................................................................................. 59

4 Contents SPRUE30B – September 2006

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List of Figures

1 MMC/SD Card Controller Block Diagram ............................................................................... 10

2 MMC/SD Controller Interface Diagram .................................................................................. 11

3 MMC Configuration and SD Configuration Diagram ................................................................... 11

4 MMC/SD Controller Clocking Diagram .................................................................................. 12

5 MMC/SD Mode Write Sequence Timing Diagram ..................................................................... 14

6 MMC/SD Mode Read Sequence Timing Diagram ..................................................................... 15

7 FIFO Operation Diagram .................................................................................................. 16

8 Little-Endian Access to MMCDXR/MMCDRR from the ARM CPU or the EDMA .................................. 17

9 Big-Endian Access to MMCDXR/MMCDRR from the ARM CPU or the EDMA .................................... 18

10 FIFO Operation During Card Read Diagram ........................................................................... 20

11 FIFO Operation During Card Write Diagram ........................................................................... 22

12 MMC Card Identification Procedure ..................................................................................... 30

13 SD Card Identification Procedure ........................................................................................ 31

14 MMC/SD Mode Single-Block Write Operation .......................................................................... 33

15 MMC/SD Mode Single-Block Read Operation .......................................................................... 35

16 MMC/SD Multiple-Block Write Operation ............................................................................... 37

17 MMC/SD Mode Multiple-Block Read Operation ........................................................................ 39

18 MMC Control Register (MMCCTL) ....................................................................................... 41

19 MMC Memory Clock Control Register (MMCCLK) ..................................................................... 42

20 MMC Status Register 0 (MMCST0) ...................................................................................... 43

21 MMC Status Register 1 (MMCST1) ...................................................................................... 45

22 MMC Interrupt Mask Register (MMCIM) ................................................................................ 46

23 MMC Response Time-Out Register (MMCTOR) ....................................................................... 47

24 MMC Data Read Time-Out Register (MMCTOD) ...................................................................... 48

25 MMC Block Length Register (MMCBLEN) .............................................................................. 49

26 MMC Number of Blocks Register (MMCNBLK) ........................................................................ 50

27 MMC Number of Blocks Counter Register (MMCNBLC) .............................................................. 50

28 MMC Data Receive Register (MMCDRR)............................................................................... 51

29 MMC Data Transmit Register (MMCDXR) .............................................................................. 51

30 MMC Command Register (MMCCMD) .................................................................................. 52

31 Command Format .......................................................................................................... 53

32 MMC Argument Register (MMCARGHL) ................................................................................ 54

33 MMC Response Register 0 and 1 (MMCRSP01) ...................................................................... 55

34 MMC Response Register 2 and 3 (MMCRSP23) ...................................................................... 55

35 MMC Response Register 4 and 5 (MMCRSP45) ...................................................................... 55

36 MMC Response Register 6 and 7 (MMCRSP67) ...................................................................... 55

37 MMC Data Response Register (MMCDRSP) .......................................................................... 57

38 MMC Command Index Register (MMCCIDX) .......................................................................... 57

39 MMC FIFO Control Register (MMCFIFOCTL) .......................................................................... 58

SPRUE30B – September 2006 List of Figures 5

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List of Tables

1 MMC/SD Controller Pins Used in Each Mode .......................................................................... 13

2 MMC/SD Mode Write Sequence ......................................................................................... 14

3 MMC/SD Mode Read Sequence ......................................................................................... 15

4 Description of MMC/SD Interrupt Requests ............................................................................ 27

5 Multimedia Card/Secure Digital (MMC/SD) Card Controller Registers .............................................. 40

6 MMC Control Register (MMCCTL) Field Descriptions................................................................. 41

7 MMC Memory Clock Control Register (MMCCLK) Field Descriptions .............................................. 42

8 MMC Status Register 0 (MMCST0) Field Descriptions ............................................................... 43

9 MMC Status Register 1 (MMCST1) Field Descriptions ............................................................... 45

10 MMC Interrupt Mask Register (MMCIM) Field Descriptions .......................................................... 46

11 MMC Response Time-Out Register (MMCTOR) Field Descriptions ................................................ 47

12 MMC Data Read Time-Out Register (MMCTOD) Field Descriptions ................................................ 48

13 MMC Block Length Register (MMCBLEN) Field Descriptions ........................................................ 49

14 MMC Number of Blocks Register (MMCNBLK) Field Descriptions .................................................. 50

15 MMC Number of Blocks Counter Register (MMCNBLC) Field Descriptions ....................................... 50

16 MMC Data Receive Register (MMCDRR) Field Descriptions ........................................................ 51

17 MMC Data Transmit Register (MMCDXR) Field Descriptions ........................................................ 51

18 MMC Command Register (MMCCMD) Field Descriptions ............................................................ 52

19 Command Format .......................................................................................................... 53

20 MMC Argument Register (MMCARGHL) Field Descriptions ......................................................... 54

21 R1, R3, R4, R5, or R6 Response (48 Bits) ............................................................................. 56

22 R2 Response (136 Bits) ................................................................................................... 56

23 MMC Data Response Register (MMCDRSP) Field Descriptions .................................................... 57

24 MMC Command Index Register (MMCCIDX) Field Descriptions .................................................... 57

25 MMC FIFO Control Register (MMCFIFOCTL) Field Descriptions ................................................... 58

A-1 Document Revision History ............................................................................................... 59

6 List of Tables SPRUE30B – September 2006

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Preface

SPRUE30B – September 2006

Read This First

About This Manual

This manual describes the multimedia card (MMC)/secure digital (SD) card controller in the

TMS320DM644x Digital Media System-on-Chip (DMSoC). The MMC/SD card is used in a number of

applications to provide removable data storage. The MMC/SD controller provides an interface to external

MMC and SD cards. The MMC/SD protocol performs the communication between the MMC/SD controller

and MMC/SD card(s).

Notational Conventions

This document uses the following conventions.

• Hexadecimal numbers are shown with the suffix h. For example, the following number is 40

hexadecimal (decimal 64): 40h.

• Registers in this document are shown in figures and described in tables.

– Each register figure shows a rectangle divided into fields that represent the fields of the register.

Each field is labeled with its bit name, its beginning and ending bit numbers above, and its

read/write properties below. A legend explains the notation used for the properties.

– Reserved bits in a register figure designate a bit that is used for future device expansion.

Related Documentation From Texas Instruments

The following documents describe the TMS320DM644x Digital Media System-on-Chip (DMSoC). Copies

of these documents are available on the Internet at www.ti.com . Tip: Enter the literature number in the

search box provided at www.ti.com.

The current documentation that describes the DM644x DMSoC, related peripherals, and other technical

collateral, is available in the C6000 DSP product folder at: www.ti.com/c6000 .

SPRUE14 — TMS320DM644x DMSoC ARM Subsystem Reference Guide. Describes the ARM

subsytem in the TMS320DM644x Digital Media System-on-Chip (DMSoC). The ARM subsystem is

designed to give the ARM926EJ-S (ARM9) master control of the device. In general, the ARM is

responsible for configuration and control of the device; including the DSP subsystem, the video

processing subsystem, and a majority of the peripherals and external memories.

SPRUE15 — TMS320DM644x DMSoC DSP Subsystem Reference Guide. Describes the digital signal

processor (DSP) subsystem in the TMS320DM644x Digital Media System-on-Chip (DMSoC).

SPRUE19 — TMS320DM644x DMSoC Peripherals Overview Reference Guide. Provides an overview

and briefly describes the peripherals available on the TMS320DM644x Digital Media

System-on-Chip (DMSoC).

SPRAA84 — TMS320C64x to TMS320C64x+ CPU Migration Guide. Describes migrating from the

Texas Instruments TMS320C64x digital signal processor (DSP) to the TMS320C64x+ DSP. The

objective of this document is to indicate differences between the two cores. Functionality in the

devices that is identical is not included.

SPRU732 — TMS320C64x/C64x+ DSP CPU and Instruction Set Reference Guide. Describes the CPU

architecture, pipeline, instruction set, and interrupts for the TMS320C64x and TMS320C64x+ digital

signal processors (DSPs) of the TMS320C6000 DSP family. The C64x/C64x+ DSP generation

comprises fixed-point devices in the C6000 DSP platform. The C64x+ DSP is an enhancement of

the C64x DSP with added functionality and an expanded instruction set.

SPRUE30B – September 2006 Preface 7

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Related Documentation From Texas Instruments

SPRU871 — TMS320C64x+ DSP Megamodule Reference Guide. Describes the TMS320C64x+ digital

signal processor (DSP) megamodule. Included is a discussion on the internal direct memory access

(IDMA) controller, the interrupt controller, the power-down controller, memory protection, bandwidth

management, and the memory and cache.

SPRAAA6 — EDMA v3.0 (EDMA3) Migration Guide for TMS320DM644x DMSoC. Describes migrating

from the Texas Instruments TMS320C64x digital signal processor (DSP) enhanced direct memory

access (EDMA2) to the TMS320DM644x Digital Media System-on-Chip (DMSoC) EDMA3. This

document summarizes the key differences between the EDMA3 and the EDMA2 and provides

guidance for migrating from EDMA2 to EDMA3.

Trademarks

SD is a trademark of SanDisk.

8 Read This First SPRUE30B – September 2006

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1 Introduction

1.1 Purpose of the Peripheral

1.2 Features

1.3 Functional Block Diagram

User's Guide

SPRUE30B – September 2006

Multimedia Card (MMC)/Secure Digital (SD) Card

Controller

This document describes the multimedia card (MMC)/secure digital (SD) card controller in the

TMS320DM644x Digital Media System-on-Chip (DMSoC).

A number of applications use the multimedia card (MMC)/secure digital (SD) card to provide removable

data storage. The MMC/SD card controller provides an interface to external MMC and SD cards. The

communication between the MMC/SD card controller and MMC/SD card(s) is performed according to the

MMC/SD protocol.

The MMC/SD card controller has the following features:

• Supports interface to multimedia cards (MMC)

• Supports interface to secure digital (SD) memory cards

• Ability to use the MMC/SD protocol

• Programmable frequency of the clock that controls the timing of transfers between the MMC/SD

controller and memory card

• 256-bit read/write FIFO to lower system overhead

• Signaling to support enhanced direct memory access (EDMA) transfers (slave)

• 20 MHz maximum clock to MMC (specification 3.31)

• 50 MHz maximum clock to SD (specification version 1.1)

The MMC/SD card controller transfers data between the ARM and the EDMA controller on one side and

the MMC/SD card on the other side, as shown in Figure 1 . This means you have a choice of performing

data transfers using the CPU or EDMA as a mechanism to move data between the device memory and

the FIFO. The ARM and the EDMA controller can read from or write to the data in the card by accessing

the registers in the MMC/SD controller.

SPRUE30B – September 2006 Multimedia Card (MMC)/Secure Digital (SD) Card Controller 9

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Status

and

registers

DMA requests

Interrupts

ARM CPU

FIFO

MMC/SD

interface

CLK

divider

MMC/SD

card

interface

1.4 Supported Use Case Statement

1.5 Industry Standard(s) Compliance Statement

2 Peripheral Architecture

Peripheral Architecture

Figure 1. MMC/SD Card Controller Block Diagram

The MMC/SD card controller supports the following user cases:

• MMC/SD card identification

• MMC/SD single-block read using CPU

• MMC/SD single-block read using EDMA

• MMC/SD single-block write using CPU

• MMC/SD single-block write using EDMA

• MMC/SD multiple-block read using CPU

• MMC/SD multiple-block read using EDMA

• MMC/SD multiple-block write using CPU

• MMC/SD multiple-block write using EDMA

The MMC/SD card controller supports the following industry standards (with the exception noted below):

• MMC (Multimedia Card) Specification V3.31

• SD (Secure Digital) Physical Layer Specification V1.1

The information in this document assumes that you are familiar with these standards.

The MMC/SD controller does not support the SPI mode of operation.

The MMC/SD controller uses the MMC/SD protocol to communicate with the MMC/SD cards. You can

configure the MMC/SD controller to work as an MMC or SD controller, based on the type of card the

controller is communicating with. Figure 2 summarizes the MMC/SD mode interface. Figure 3 illustrates

how the controller interfaces to the cards in MMC/SD mode.

In the MMC/SD mode, the MMC controller supports one or more MMC/SD cards. Regardless of the

number of cards connected, the MMC/SD controller selects one by using identification broadcast on the

data line. The following MMC/SD controller pins are used:

• CMD: This pin is used for two-way communication between the connected card and the MMC/SD

controller. The MMC/SD controller transmits commands to the card and the memory card drives

responses to the commands on this pin.

• DAT0 or DAT0-3: MMC cards only use one data line (DAT0) and SD cards use one or four data lines.

The number of DAT pins (the data bus width) is set by the WIDTH bit in the MMC control register

(MMCCTL), see Section 4.1 ).

• CLK: This pin provides the clock to the memory card from the MMC/SD controller.

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Native packets

Native

signals

CMD

CLK

DAT0 or DAT0−3

MMC/SD

controller

ARM

EDMA

Memory

MMCs or SD cards

SD_CLK

SD_CMD

SD_DATA0

SD_DATA1

SD_DATA2

SD_DATA3

MMC/SD controller MMC and SD (1−bit mode)

CLK

CMD

DAT0

MMC/SD configuration

MMC/SD controller

SD_DATA0

SD_CMD

SD_CLK

DAT0

CMD

SD card (4−bit mode)

CLK

SD_DATA2

SD_DATA3

SD_DATA1

SD configuration

DAT1

DAT2

DAT3

Peripheral Architecture

Figure 2. MMC/SD Controller Interface Diagram

Figure 3. MMC Configuration and SD Configuration Diagram

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2.1 Clock Control

MMCCLK

(CLKRT)

Function clock for

MMC/SD controller

MMC/SD

input clock

card

MMC/SD

Memory clock

on CLK pin

Peripheral Architecture

There are two clocks, the function clock and the memory clock, in the MMC/SD controller (Figure 4 ).

The function clock determines the operational frequency of the MMC/SD controller and is the input clock

to the MMC/SD card(s). The MMC/SD controller is capable of operating with a function clock up to

100 MHz.

The memory clock appears on the SD_CLK pin of the MMC/SD controller interface. The memory clock

controls the timing of communication between the MMC/SD controller and the connected memory card.

The memory clock is generated by dividing the function clock in the MMC/SD controller. The divide-down

value is set by CLKRT bits in the MMC memory clock control register (MMCCLK) and is determined by the

following equation:

memory clock frequency = function clock frequency/(2 × (CLKRT + 1))

Figure 4. MMC/SD Controller Clocking Diagram

(1) Maximum memory clock frequency in MMC card can be 20 MHz.

(2) Maximum memory clock frequency in SD card can be 50 MHz.

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2.2 Signal Descriptions

2.3 Protocol Descriptions

2.3.1 MMC/SD Mode Write Sequence

Peripheral Architecture

Table 1 shows the MMC/SD controller pins that each mode uses. The MMC/SD protocol uses the clock,

command (two-way communication between the MMC controller and memory card), and data (DAT0 for

MMC card, DAT0-3 for SD card) pins.

Table 1. MMC/SD Controller Pins Used in Each Mode

Function

MMC and SD (1-bit mode) SD (4-bit mode)

Pin Type

(1)

Communications Communications

CLK O Clock line Clock line

CMD I/O Command line Command line

DAT0 I/O Data line 0 Data line 0

DAT1 I/O (Not used) Data line 1

DAT2 I/O (Not used) Data line 2

DAT3 I/O (Not used) Data line 3

(1)

I = input to the MMC controller; O = output from the MMC controller.

The MMC/SD controller follows the MMC/SD protocol for completing any kind of transaction with the

multimedia card and secure digital cards. For more detailed information, refer to the supported MMC and

SD specifications in Section 1.5 .

Figure 5 and Table 2 show the signal activity when the MMC/SD controller is in the MMC/SD mode and is

writing data to a memory card. The same block length must be defined in the MMC/SD controller and in

the memory card before initiating a data write. In a successful write protocol sequence, the following steps

occur:

• The MMC/SD controller requests the CSD content.

• The card receives the command and sends the content of the CSD register as its response.

• If the desired block length, WRITE_BL_LEN value, is different from the default value determined from

the response, the MMC/SD controller sends the block length command.

• The card receives the command and sends responses to the command.

• The MMC/SD controller requests the card to change states from standby to transfer.

• The card receives the command and sends responses to the command.

• The MMC/SD controller sends a write command to the card.

• The card receives the command and sends responses to the command.

• The MMC/SD controller sends a block of data to the card.

• The card sends the CRC status to the MMC/SD controller.

• The card sends a low BUSY bit until all of the data has been programmed into the flash memory inside

the card.

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2 CRC bytes

Busy

low

Start

bit

End

bit

Start

bit

End

bit

CMD

Data

CLK

2.3.2 MMC/SD Mode Read Sequence

Peripheral Architecture

Figure 5. MMC/SD Mode Write Sequence Timing Diagram

Table 2. MMC/SD Mode Write Sequence

Portion of the

Sequence Description

WR CMD Write command: A 6-byte WRITE_BLOCK command token is sent from the ARM to the card.

CMD RSP Command response: The card sends a 6-byte response of type R1 to acknowledge the WRITE_BLOCK to the

ARM.

DAT BLK Data block: The ARM writes a block of data to the card. The data content is preceded by one start bit and is

followed by two CRC bytes and one end bit.

CRC STAT CRC status: The card sends a one byte CRC status information, which indicates to the ARM whether the data has

been accepted by the card or rejected due to a CRC error. The CRC status information is preceded by one start

bit and is followed by one end bit.

BSY BUSY bit: The CRC status information is followed by a continuous stream of low busy bits until all of the data has

been programmed into the flash memory on the card.

Figure 6 and Table 3 show the signal activity when the MMC controller is in the MMC/SD mode and is

reading data from a memory card. The same block length must be defined in the MMC controller and in

the memory card before initiating a data read. In a successful read protocol sequence, the following steps

occur:

• The MMC/SD controller requests for the CSD content.

• The card receives the command and sends the content of the CSD register as its response.

• If the desired block length, READ_BL_LEN value, is different from the default value determined from

the response, the MMC/SD controller sends the block length command.

• The card receives the command and sends responses to the command.

• The MMC/SD controller requests the card to change state from stand-by to transfer.

• The card receives the command and sends responses to the command.

• The MMC/SD controller sends a read command to the card.

• The card drives responses to the command.

• The card sends a block of data to the ARM.

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Start

bit

End

bit

CMD

Data

CLK

1 transfer

source bit

2 CRC

bytes

2.4 Data Flow in the Input/Output FIFO

Peripheral Architecture

Figure 6. MMC/SD Mode Read Sequence Timing Diagram

Table 3. MMC/SD Mode Read Sequence

Portion of the

Sequence Description

RD CMD Read command: A 6-byte READ_SINGLE_BLOCK command token is sent from the ARM to the card.

CMD RSP Command response: The card sends a response of type R1 to acknowledge the READ_SINGLE_BLOCK

command to the ARM.

DAT BLK Data block: The card sends a block of data to the ARM. The data content is preceded by a start bit and is

followed by two CRC byte and an end bit.

The MMC/SD controller contains a single 256-bit FIFO that is used for both reading data from the memory

card and writing data to the memory card (see Figure 7 ). The FIFO is organized as 32 eight-bit entries.

The conversion from the 32-bit bus to the byte format of the FIFO follows the little-endian convention

(details are provided in later sections). The read and write FIFOs act as an interim location to store data

transferred from/to the card momentarily via the CPU or EDMA. The FIFO includes logic to generate

EDMA events and interrupts based on the amount of data in the FIFO and a programmable number of

bytes received/transmitted. Flags are set when the FIFO is full or empty.

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ARM/EDMA reads/writes

Write Read

FIFO

8−bit x 32

(256−bit)

FIFO

EDMA event

128 or 256 bit

EDMA event

the end of a

transfer

Pointer increment

or decrease

Pointer increment

or decrease

FIFO

16−bit DXR 16−bit DRR

16−bit DXR

shifter

16−bit DRR

shifter

DXR DRR

EDMA

request

is created

Transmission of data

Step 1: Set FIFO reset

Step 2: Set FIFO direction

Step 4: CPU driven transaction:

Fill the FIFO by writing to

MMCDXR (only first time)

Step 5: EDMA send xmit data

Step 6: If DXR ready is active,

FIFO −> 16−bit DXR

Reception of data

Step 3:

Step 2:

Step 1: Set FIFO reset

Set FIFO direction

If DRR ready is active,

16−bit DRR −> FIFO

Step 6: EDMA read reception data

Step 4: EDMA driven transaction

Step 5: DRRDYINT interrupt occur

Step 3: EDMA driven transaction

or every 128 or 256−bits

transmitted and DXRDYINT

interrupt is generated

when FIFO every 128 or

256−bits of data received

by FIFO

Peripheral Architecture

A high-level operational description is as follows:

• Data is written to the FIFO through the MMC data transmit register (MMCDXR). Data is read from the

FIFO through the MMC data receive register (MMCDRR). This is true for both the CPU and EDMA

driven transactions; however, for the EDMA transaction, the EDMA access to the FIFO is transparent.

• The ACCWD bits in the MMC FIFO control register (MMCFIFOCTL) determines the behavior of the

FIFO full (FIFOFUL) and FIFO empty (FIFOEMP) status flags in the MMC status register 1 (MMCST1):

– If ACCWD = 00b:

• FIFO full is active when the write pointer + 4 > read pointer

• FIFO empty is active when the write pointer - 4 < read pointer

– If ACCWD = 01b:

• FIFO full is active when the write pointer + 3 > read pointer

• FIFO empty is active when the write pointer - 3 < read pointer

– If ACCWD = 10b:

• FIFO full is active when the write pointer + 2 > read pointer

• FIFO empty is active when the write pointer - 2 < read pointer

– If ACCWD = 11b:

• FIFO full is active when the write pointer + 1 > read pointer

• FIFO empty is active when the write pointer - 1 < read pointer

Figure 7. FIFO Operation Diagram

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2.5 Data Flow in the Data Registers (MMCDRR and MMCDXR)

1st

2nd

3rd

4th

3

4th 3rd 2nd 1st

Support byten = ”1111”

Support byten = ”0111”

3rd

2nd

1st

3

3rd 2nd 1st

Support byten = ”0011”

1st

2nd

3

2nd 1st

0

Support byten = ”0001”

1st

3

1st

0

FIFO MMCDRR or MMCDXR registers

Peripheral Architecture

The CPU or EDMA controller can read 32 bits at a time from the FIFO by reading the MMC data receive

register (MMCDRR) and write 32 bits at a time to the FIFO by writing to the MMC data transmit register

(MMCDXR). However, since the memory card is an 8-bit device, it transmits or receives one byte at a

time. Figure 8 and Figure 9 show how the data-size difference is handled by the data registers in

little-endian and big-endian configurations, respectively.

Figure 8. Little-Endian Access to MMCDXR/MMCDRR from the ARM CPU or the EDMA

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1st

2nd

3rd

4th

3

4th3rd2nd1st

Support byten = ”1111”

Support byten = ”1110”

3rd

2nd

1st

3

3rd2nd1st

Support byten = ”1100”

1st

2nd

3

2nd1st

0

Support byten = ”1000”

1st

3

1st

0

Peripheral Architecture

Figure 9. Big-Endian Access to MMCDXR/MMCDRR from the ARM CPU or the EDMA

18 Multimedia Card (MMC)/Secure Digital (SD) Card Controller SPRUE30B – September 2006

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2.6 FIFO Operation During Card Read Operation

2.6.1 EDMA Reads

2.6.2 CPU Reads

Peripheral Architecture

The FIFO controller manages the activities of reading the data in from the card and issuing EDMA read

events. Each time an EDMA read event is issued, an EDMA read request interrupt generates.

Figure 10 provides details of the FIFO controllers operation. As data is received from the card, it is read

into the FIFO. When the number of bytes of data received is equal to the level set by the FIFOLEV bits in

MMCFIFOCTL, an EDMA read event is issued and new EDMA events are disabled until the EDMA is

done with the transfer issued by the current event. Data is read from the FIFO by way of MMCDRR. The

FIFO controller continues to read in data from the card while checking for the EDMA event to occur or for

the FIFO to become full. Once the EDMA event finishes, new EDMA events are enabled. If the FIFO fills

up, the FIFO controller stops the MMC/SD controller from reading any more data until the FIFO is no

longer full.

An EDMA read event generates when the last data arrives, as determined by the MMC block length

register (MMCBLEN) and the MMC number of blocks register (MMCNBLK) settings. This EDMA event

flushes all of the data that was read from the card from the FIFO.

Each time an EDMA read event generates, an interrupt (DRRDYINT) generates and the DRRDY bit in the

MMC status register 0 (MMCST0) is also set.

The system CPU can also directly read the card data by reading the MMC data receive register

(MMCDRR). The MMC/SD peripheral supports reads that are 1, 2, 3, or 4 bytes wide as, shown in

Figure 8 and Figure 9 .

As data is received from the card, it is read into the FIFO. When the number of bytes of data received is

equal to the level set by the FIFOLEV bits in MMCFIFOCTL, a DRRDYINT interrupt is issued and the

DRRDY bit in the MMC status register 0 (MMCST0) is set. Upon receiving the interrupt, the CPU quickly

reads out the bytes received (equal to the level set by the FIFOLEV bits). A DRRDYINT interrupt also

generates when the last data arrives as determined by the MMC block length register (MMCBLEN) and

the MMC numbers of blocks register (MMCNBLK) settings.

SPRUE30B – September 2006 Multimedia Card (MMC)/Secure Digital (SD) Card Controller 19

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FIFO Check1/Start

FIFO

full

?

Counter

=FIFOLEV

?

Yes

No

Capture data,

no DMA pending

Increment counter

No

Yes

Generate DMA

Reset counter

FIFO check 2

Yes

No

?

full

FIFO

No

=FIFOLEV

?

Counter

Increment counter

DMA

Capture data,

done

?

DMA

No

Yes

Generate DMA

Reset counter

Idle, DMA pending

DMA

No

done

?

Peripheral Architecture

Figure 10. FIFO Operation During Card Read Diagram

Multimedia Card (MMC)/Secure Digital (SD) Card Controller20 SPRUE30B – September 2006

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Texas Instruments TMS320DM644x User manual

Texas Instruments TMS320DM644x User manual

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