AN1475
APPLICATION NOTE
DEVELOPING AN ST7265x
MASS STORAGE APPLICATION
By Microcontroller Division Applications
INTRODUCTION
This application note describes how to develop a USB Mass Storage application using an
ST7265x microcontroller.
The proposed solution includes a generic USB Mass Storage Layer (MSL) compliant with the
USB Mass Storage Class that can be used for all types of storage media (FLASH memory
cards, hard disk drive, etc.) and a dedicated Media Access Layer (MAL) add-in for each type
of storage media.
The MSL and the MAL modules are available to ST customers on request. Contact your ST
sales office to obtain the ST7265 Mass Storage software.
The MSL and the MAL must be considered as function libraries and therefore cannot be modified by the user. The software interfaces of these function libraries provide the user with the
required flexibility for designing his application:
– type and number of media,
– insertion/withdrawal management,
– protection management,
– user interface.
Note that the MAL requires the use of certain fixed MCU pins to interface with the various mediums. As a result, a specific application hardware configuration is required when using the
MAL.
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DEVELOPING AN ST7265x MASS STORAGE APPLICATION
1 SOFTWARE ARCHITECTURE
The ST7265 software is designed in modules. Each module has a unique and clearly defined
interface. This architecture enables the user to easily replace any module and to reuse the individual module in other projects. This architecture provides maximum flexibility so users are
able to customize their application as they want. The module software design is showed in
Figure 1.
USB Mass Storage Layer
User Application
Status
Information
Media Configuration
Media Access Layer
Storage
Media
= ST provided module
Medium-dependent
LUN Assignment
Medium-independent
Figure 1. ST7265 Mass Storage Application Architecture
All the components described above are grouped into a project. The “Status Information” interface enables the user to monitor the execution of the software. The “Media Configuration”
interface enables the user to customize the application configuration.
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DEVELOPING AN ST7265x MASS STORAGE APPLICATION
2 PROJECT CONTENT
Files required for the various modules are grouped into different directories. Most files are
user application independent; i.e. they are not designed to be modified by the user application.
Other files are application dependent and can be modified by the user. Table 1 explains the
usage of the files included in the project.
Table 1. Application Files
Directory
Path/File
Usage
Application-related routines (called from main.c) to be
Appli.c, Appli.h
developed by the user.
These files contain all the descriptors for the USB enuDescript.c, Descript.h
meration. These files are designed to be modified by
the user depending on the user application.
MCL
This file contains the global Media Access Library setMAL_Func.c
tings. These files are designed to be modified by the
(Application
user depending on the user application.
specific)
Definitions of the software interface described in the
Mconfig.h
document. These files are designed to be modified by
the user depending on the user application.
Groups all interrupt routines. These files areto be modInt_7265.c, Int_7265.h
ified by the user depending on the user application.
Conditional compilation definitions. This file is used to
Condconfigure the USB behaviour. This file is not designed
comp.h
to be modified by the user.
Micro
Main software entry point. This file is not designed to be
Main.c
modified by the user (see Appli.c)
MAS
User_lib.c, USB routines related to this application. These files are
Sto
User_lib.h not designed to be modified by the user.
Media Access Library. These files are not designed to
MAL
be modified by the user.
Files related to the standard Mass Storage operation.
Class
All files
These files are not designed to be modified by the user.
Files related to the standard USB operations. These
USBlib
All files.
files are not designed to be modified by the user.
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DEVELOPING AN ST7265x MASS STORAGE APPLICATION
3 USING THE MASS STORAGE LIBRARIES
3.1 MAXIMUM NUMBER OF LOGICAL UNITS
A constant representing the number of medium slots implemented in the application project
must be defined by the user application.
#defineMAX_LUN
The valid range of this variable is between 0 and 15. The MAX_LUN value is one less than the
number of slots; for example, if the MAX_LUN value is 3, there are 4 slots.
3.2 MEDIA SELECTION
A Media Access Layer (MAL) add-in for each type of storage media is provided by STMicroelectronics. Several functions are provided with this interface and are called using a single entry
function. To assign logical units to each type of media, an array pointing to the entry function
must be provided by the application.
const void (*Mal_Func[MAX_LUN+1])();
The medium is identified by the index of this array. For example, the function array is assigned
as:
extern void MAL_SMC_Funcs(void);
extern void MAL_MMC_Funcs(void);
;
include SMC support in MAL
include MMC support in MAL
Assign LUNs (Logical Unit Numbers) in ascending order starting with LUN0
const void (*Mal_Func[MAX_LUN+1])() = {
MAL_SMC_Funcs,
MAL_MMC_Funcs
};
In the above example, the MAL_SMC_Funcs() function is provided with the MAL for SMC and
the MAL_MMC_Funcs() function is provided with the MAL for MMC. Thus, the SMC device will
be identified as LUN0 and the MMC device will be identified as LUN1.
3.3 INTERFACE DESCRIPTION
3.3.1 Hardware Interfaces
3.3.1.1 USB Interface
The pins used for the USB connection are defined in the ST7265x product datasheet.
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3.3.1.2 Compact Flash Card 8-bit Memory Mode
Some hardware interface pins are fixed by the MAL firmware as shown in the table below.
CompactFlashBus
ST7265x Pin
D0
D1
D2
D3
D4
D5
D6
D7
A0
A1
A2
RE
WE
PB0
PB1
PB2
PB3
PB4
PB5
PB6
PB7
PA0
PA1
PA2
PA3
PA5
Other pins are user definable in the Media Configuration Module (Mconfig.c)
In this configuration, pins PA4, PA6 and PA7 can only be used as inputs (no interrupt capability).
3.3.1.3 SmartMediaCard Interface
Some hardware interface pins are fixed by the MAL firmware as shown in the table below.
Other pins are user definable in the Media Configuration Module (Mconfig.c)
SmartMediaBus
ST7265x Pin
D0
PB0
D1
PB1
D2
PB2
D3
PB3
D4
PB4
D5
PB5
D6
PB6
D7
PB7
ALE
PA2
WE
PA1
RE
PA3
RBUSY
PA4
CLE
PA0
In this configuration, pins PA5, PA6 and PA7 can only be used as inputs (no interrupt capability).
3.3.1.4 MultiMediaCard Interface
This interface is used for MultimediaCard (MMC), Secure Digital (SD) Card in MMC mode and
Hitachi cards.
Some hardware interface pins are fixed by the MAL firmware as shown in the table below.
Other pins are user definable in the Media Configuration Module (Mconfig.c).
MMC Bus
ST7265x Pin
DATA
PE6
COMMAND
PE5
CLOCK
PE7
3.3.1.5 Sony Stick
Some hardware interface pins are fixed by the MAL firmware as shown in the table below.
Other pins are user definable in the Media Configuration Module (Mconfig.c).
Sony Stick Bus
ST7265x Pin
BS
PC1
DATA
PC2
CLOCK
PC3
3.3.2 Software Interfaces
The software interfaces described in this document are not media specific.
3.3.2.1 Status Information
Medium Capacity
The capacity of each medium can be read from the Medium_Capacity[ ] variable
DWORD Medium_Capacity[MAX_LUN+1];
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The medium is identified by the index of this array.
Current Operation
The MAL_State variable gives the internal state of the current operation. Read, write, format
and verify operations are indicated with this variable. The following values are available for the
MAL_State function:
#define
#define
#define
#define
#define
#define
#define
MAL_IDLE
MAL_READING
MAL_WRITING
MAL_VERIFYING
MAL_FORMATTING
MAL_MEM_READING
MAL_MEM_WRITING
0
1
2
3
4
5
6
//
//
//
//
//
//
//
no operation
upload data to USB
download data from USB
verifying
formatting
reading data to RAM
writing data from RAM
Active Medium
The MAL_Mediano variable identifies the medium that is currently accessed.
unsigned charMAL_Mediano;
3.3.2.2 Media Configuration
This interface is related with the physical and electrical configuration of the media device itself.
Through this interface, the user must provide certain information to the MAL or carry out certain functions required by the MAL. Indeed, some functions depend on the user hardware or
software implementation, and can therefore not be directly carried out by the MAL.
None of the functions defined in this section can be omitted. Even if no action is taken, the
function must be defined.
Existence of the Medium
There are two operations in this category, medium existence testing and the medium removal
interrupt.
Medium existence testing should be done by the user application. The application calls the
MAL_Medium_Plug() interrupt to inform the MAL library that a medium is present:
void MAL_Medium_Plug(unsigned char slot)
The slot parameter indicates which medium is present.
The user application should use an interrupt routine to monitor medium removal. When the
medium is removed, an interrupt is triggered and an application-defined interrupt routine is
called. In this interrupt routine, the user application calls the MAL_Medium_Removing() function to notify the MAL that the medium is removed. The parameter indicates the slot where the
medium removal has occurred. The MAL guarantees that the MAL_Medium_Removing()
function returns to the medium removal interrupt routine as soon as possible. The template of
this function is:
void MAL_Medium_Removing(char Index);
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The index parameter indicates the medium that has been removed.
Selection of the Medium
Medium select and deselect operations are defined as follows:
#define
#define
SELECT()
DESELECT()
The index parameter indicates the medium to be selected or deselected.
The evaluation values of these two operations are not important. The calling function is used
to detect the existence of the medium.
The SELECT() function enables the chip select bit of the selected device, and the DESELECT() function disables the chip select bit of the selected device. The application can (optional) indicate the media being accessed by switching ON an LED in the SELECT() function
and switching OFF the LED in the DESELECT() function.
Once the SELECT() function is executed, the media is ready to be accessed.
Detection of the Write Protection
The testing of the write protection is defined as:
#define
isWRITE_PROTECT()
The index parameter indicates the medium to be tested.
The value of this operation is non-zero if the medium is write-protected, otherwise a zero is
emitted.
Medium Initialization
The media ready function is initialized by the user application. For example, the user application must verify that the medium access is authorized. Either the MAL or the MSL assumes
that the medium is powered on and ready to be operated after the SELECT() function is executed.
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