$treeview $search $mathjax $extrastylesheet

avr-libc  2.0.0 $projectbrief

$projectbrief

$searchbox

AVR Libc Home Page					AVR Libc Development Pages
Main Page	User Manual	Library Reference	FAQ	Example Projects

lock.h

Go to the documentation of this file.

/* Copyright (c) 2007, Atmel Corporation
   All rights reserved.

   Redistribution and use in source and binary forms, with or without
   modification, are permitted provided that the following conditions are met:

   * Redistributions of source code must retain the above copyright
     notice, this list of conditions and the following disclaimer.

   * Redistributions in binary form must reproduce the above copyright
     notice, this list of conditions and the following disclaimer in
     the documentation and/or other materials provided with the
     distribution.

   * Neither the name of the copyright holders nor the names of
     contributors may be used to endorse or promote products derived
     from this software without specific prior written permission.

  THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
  AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
  IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
  ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
  LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
  SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
  INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
  CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
  ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  POSSIBILITY OF SUCH DAMAGE. */

/* $Id$ */

/* avr/lock.h - Lock Bits API */

#ifndef _AVR_LOCK_H_
#define _AVR_LOCK_H_  1


/** \file */
/** \defgroup avr_lock <avr/lock.h>: Lockbit Support

    \par Introduction

    The Lockbit API allows a user to specify the lockbit settings for the 
    specific AVR device they are compiling for. These lockbit settings will be 
    placed in a special section in the ELF output file, after linking.

    Programming tools can take advantage of the lockbit information embedded in
    the ELF file, by extracting this information and determining if the lockbits
    need to be programmed after programming the Flash and EEPROM memories.
    This also allows a single ELF file to contain all the
    information needed to program an AVR. 

    To use the Lockbit API, include the <avr/io.h> header file, which in turn
    automatically includes the individual I/O header file and the <avr/lock.h>
    file. These other two files provides everything necessary to set the AVR
    lockbits.
    
    \par Lockbit API
    
    Each I/O header file may define up to 3 macros that controls what kinds
    of lockbits are available to the user.
    
    If __LOCK_BITS_EXIST is defined, then two lock bits are available to the
    user and 3 mode settings are defined for these two bits.
    
    If __BOOT_LOCK_BITS_0_EXIST is defined, then the two BLB0 lock bits are
    available to the user and 4 mode settings are defined for these two bits.
    
    If __BOOT_LOCK_BITS_1_EXIST is defined, then the two BLB1 lock bits are
    available to the user and 4 mode settings are defined for these two bits.

    If __BOOT_LOCK_APPLICATION_TABLE_BITS_EXIST is defined then two lock bits
    are available to set the locking mode for the Application Table Section 
    (which is used in the XMEGA family).
    
    If __BOOT_LOCK_APPLICATION_BITS_EXIST is defined then two lock bits are
    available to set the locking mode for the Application Section (which is used
    in the XMEGA family).
    
    If __BOOT_LOCK_BOOT_BITS_EXIST is defined then two lock bits are available
    to set the locking mode for the Boot Loader Section (which is used in the
    XMEGA family).

    The AVR lockbit modes have inverted values, logical 1 for an unprogrammed 
    (disabled) bit and logical 0 for a programmed (enabled) bit. The defined 
    macros for each individual lock bit represent this in their definition by a 
    bit-wise inversion of a mask. For example, the LB_MODE_3 macro is defined 
    as:
    \code
    #define LB_MODE_3  (0xFC)
`   \endcode
    
    To combine the lockbit mode macros together to represent a whole byte,
    use the bitwise AND operator, like so:
    \code
    (LB_MODE_3 & BLB0_MODE_2)
    \endcode
    
    <avr/lock.h> also defines a macro that provides a default lockbit value:
    LOCKBITS_DEFAULT which is defined to be 0xFF.

    See the AVR device specific datasheet for more details about these
    lock bits and the available mode settings.
    
    A convenience macro, LOCKMEM, is defined as a GCC attribute for a 
    custom-named section of ".lock".
    
    A convenience macro, LOCKBITS, is defined that declares a variable, __lock, 
    of type unsigned char with the attribute defined by LOCKMEM. This variable
    allows the end user to easily set the lockbit data.

    \note If a device-specific I/O header file has previously defined LOCKMEM,
    then LOCKMEM is not redefined. If a device-specific I/O header file has
    previously defined LOCKBITS, then LOCKBITS is not redefined. LOCKBITS is
    currently known to be defined in the I/O header files for the XMEGA devices.

    \par API Usage Example
    
    Putting all of this together is easy:
    
    \code
    #include <avr/io.h>

    LOCKBITS = (LB_MODE_1 & BLB0_MODE_3 & BLB1_MODE_4);

    int main(void)
    {
        return 0;
    }
    \endcode
    
    Or:
    
    \code
    #include <avr/io.h>

    unsigned char __lock __attribute__((section (".lock"))) = 
        (LB_MODE_1 & BLB0_MODE_3 & BLB1_MODE_4);

    int main(void)
    {
        return 0;
    }
    \endcode
    
    
    
    However there are a number of caveats that you need to be aware of to
    use this API properly.
    
    Be sure to include <avr/io.h> to get all of the definitions for the API.
    The LOCKBITS macro defines a global variable to store the lockbit data. This 
    variable is assigned to its own linker section. Assign the desired lockbit 
    values immediately in the variable initialization.
    
    The .lock section in the ELF file will get its values from the initial 
    variable assignment ONLY. This means that you can NOT assign values to 
    this variable in functions and the new values will not be put into the
    ELF .lock section.
    
    The global variable is declared in the LOCKBITS macro has two leading 
    underscores, which means that it is reserved for the "implementation",
    meaning the library, so it will not conflict with a user-named variable.
    
    You must initialize the lockbit variable to some meaningful value, even
    if it is the default value. This is because the lockbits default to a 
    logical 1, meaning unprogrammed. Normal uninitialized data defaults to all 
    locgial zeros. So it is vital that all lockbits are initialized, even with 
    default data. If they are not, then the lockbits may not programmed to the 
    desired settings and can possibly put your device into an unrecoverable 
    state.
    
    Be sure to have the -mmcu=<em>device</em> flag in your compile command line and
    your linker command line to have the correct device selected and to have 
    the correct I/O header file included when you include <avr/io.h>.

    You can print out the contents of the .lock section in the ELF file by
    using this command line:
    \code
    avr-objdump -s -j .lock <ELF file>
    \endcode

*/


#if !(defined(__ASSEMBLER__) || defined(__DOXYGEN__))

#ifndef LOCKMEM
#define LOCKMEM  __attribute__((__used__, __section__ (".lock")))
#endif

#ifndef LOCKBITS
#define LOCKBITS unsigned char __lock LOCKMEM
#endif

/* Lock Bit Modes */
#if defined(__LOCK_BITS_EXIST)
#define LB_MODE_1  (0xFF)
#define LB_MODE_2  (0xFE)
#define LB_MODE_3  (0xFC)
#endif

#if defined(__BOOT_LOCK_BITS_0_EXIST)
#define BLB0_MODE_1  (0xFF)
#define BLB0_MODE_2  (0xFB)
#define BLB0_MODE_3  (0xF3)
#define BLB0_MODE_4  (0xF7)
#endif

#if defined(__BOOT_LOCK_BITS_1_EXIST)
#define BLB1_MODE_1  (0xFF)
#define BLB1_MODE_2  (0xEF)
#define BLB1_MODE_3  (0xCF)
#define BLB1_MODE_4  (0xDF)
#endif

#if defined(__BOOT_LOCK_APPLICATION_TABLE_BITS_EXIST)
#define BLBAT0 ~_BV(2)
#define BLBAT1 ~_BV(3)
#endif

#if defined(__BOOT_LOCK_APPLICATION_BITS_EXIST)
#define BLBA0 ~_BV(4)
#define BLBA1 ~_BV(5)
#endif

#if defined(__BOOT_LOCK_BOOT_BITS_EXIST)
#define BLBB0 ~_BV(6)
#define BLBB1 ~_BV(7)
#endif


#define LOCKBITS_DEFAULT (0xFF)

#endif  /* !(__ASSEMBLER || __DOXYGEN__) */


#endif /* _AVR_LOCK_H_ */

---