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2.1.0
Standard C library for AVR-GCC
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include
avr
lock.h
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/* Copyright (c) 2007, Atmel Corporation
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All rights reserved.
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Redistribution and use in source and binary forms, with or without
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modification, are permitted provided that the following conditions are met:
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* Redistributions of source code must retain the above copyright
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notice, this list of conditions and the following disclaimer.
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* Redistributions in binary form must reproduce the above copyright
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notice, this list of conditions and the following disclaimer in
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the documentation and/or other materials provided with the
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distribution.
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* Neither the name of the copyright holders nor the names of
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contributors may be used to endorse or promote products derived
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from this software without specific prior written permission.
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
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AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
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IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
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ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
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LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
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SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
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INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
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CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
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ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
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POSSIBILITY OF SUCH DAMAGE. */
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/* $Id: lock_8h_source.html,v 1.1.1.7 2022/01/29 09:21:56 joerg_wunsch Exp $ */
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/* avr/lock.h - Lock Bits API */
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#ifndef _AVR_LOCK_H_
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#define _AVR_LOCK_H_ 1
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/** \file */
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/** \defgroup avr_lock <avr/lock.h>: Lockbit Support
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\par Introduction
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The Lockbit API allows a user to specify the lockbit settings for the
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specific AVR device they are compiling for. These lockbit settings will be
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placed in a special section in the ELF output file, after linking.
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Programming tools can take advantage of the lockbit information embedded in
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the ELF file, by extracting this information and determining if the lockbits
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need to be programmed after programming the Flash and EEPROM memories.
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This also allows a single ELF file to contain all the
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information needed to program an AVR.
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To use the Lockbit API, include the <avr/io.h> header file, which in turn
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automatically includes the individual I/O header file and the <avr/lock.h>
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file. These other two files provides everything necessary to set the AVR
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lockbits.
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\par Lockbit API
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Each I/O header file may define up to 3 macros that controls what kinds
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of lockbits are available to the user.
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If __LOCK_BITS_EXIST is defined, then two lock bits are available to the
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user and 3 mode settings are defined for these two bits.
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If __BOOT_LOCK_BITS_0_EXIST is defined, then the two BLB0 lock bits are
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available to the user and 4 mode settings are defined for these two bits.
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If __BOOT_LOCK_BITS_1_EXIST is defined, then the two BLB1 lock bits are
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available to the user and 4 mode settings are defined for these two bits.
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If __BOOT_LOCK_APPLICATION_TABLE_BITS_EXIST is defined then two lock bits
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are available to set the locking mode for the Application Table Section
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(which is used in the XMEGA family).
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If __BOOT_LOCK_APPLICATION_BITS_EXIST is defined then two lock bits are
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available to set the locking mode for the Application Section (which is used
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in the XMEGA family).
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If __BOOT_LOCK_BOOT_BITS_EXIST is defined then two lock bits are available
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to set the locking mode for the Boot Loader Section (which is used in the
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XMEGA family).
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The AVR lockbit modes have inverted values, logical 1 for an unprogrammed
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(disabled) bit and logical 0 for a programmed (enabled) bit. The defined
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macros for each individual lock bit represent this in their definition by a
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bit-wise inversion of a mask. For example, the LB_MODE_3 macro is defined
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as:
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\code
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#define LB_MODE_3 (0xFC)
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` \endcode
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To combine the lockbit mode macros together to represent a whole byte,
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use the bitwise AND operator, like so:
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\code
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(LB_MODE_3 & BLB0_MODE_2)
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\endcode
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<avr/lock.h> also defines a macro that provides a default lockbit value:
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LOCKBITS_DEFAULT which is defined to be 0xFF.
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See the AVR device specific datasheet for more details about these
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lock bits and the available mode settings.
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A convenience macro, LOCKMEM, is defined as a GCC attribute for a
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custom-named section of ".lock".
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A convenience macro, LOCKBITS, is defined that declares a variable, __lock,
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of type unsigned char with the attribute defined by LOCKMEM. This variable
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allows the end user to easily set the lockbit data.
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\note If a device-specific I/O header file has previously defined LOCKMEM,
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then LOCKMEM is not redefined. If a device-specific I/O header file has
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previously defined LOCKBITS, then LOCKBITS is not redefined. LOCKBITS is
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currently known to be defined in the I/O header files for the XMEGA devices.
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\par API Usage Example
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Putting all of this together is easy:
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\code
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#include <avr/io.h>
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LOCKBITS = (LB_MODE_1 & BLB0_MODE_3 & BLB1_MODE_4);
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int main(void)
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{
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return 0;
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}
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\endcode
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Or:
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\code
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#include <avr/io.h>
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unsigned char __lock __attribute__((section (".lock"))) =
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(LB_MODE_1 & BLB0_MODE_3 & BLB1_MODE_4);
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int main(void)
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{
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return 0;
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}
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\endcode
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However there are a number of caveats that you need to be aware of to
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use this API properly.
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Be sure to include <avr/io.h> to get all of the definitions for the API.
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The LOCKBITS macro defines a global variable to store the lockbit data. This
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variable is assigned to its own linker section. Assign the desired lockbit
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values immediately in the variable initialization.
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The .lock section in the ELF file will get its values from the initial
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variable assignment ONLY. This means that you can NOT assign values to
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this variable in functions and the new values will not be put into the
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ELF .lock section.
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The global variable is declared in the LOCKBITS macro has two leading
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underscores, which means that it is reserved for the "implementation",
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meaning the library, so it will not conflict with a user-named variable.
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You must initialize the lockbit variable to some meaningful value, even
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if it is the default value. This is because the lockbits default to a
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logical 1, meaning unprogrammed. Normal uninitialized data defaults to all
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locgial zeros. So it is vital that all lockbits are initialized, even with
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default data. If they are not, then the lockbits may not programmed to the
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desired settings and can possibly put your device into an unrecoverable
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state.
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Be sure to have the -mmcu=<em>device</em> flag in your compile command line and
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your linker command line to have the correct device selected and to have
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the correct I/O header file included when you include <avr/io.h>.
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You can print out the contents of the .lock section in the ELF file by
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using this command line:
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\code
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avr-objdump -s -j .lock <ELF file>
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\endcode
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*/
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#if !(defined(__ASSEMBLER__) || defined(__DOXYGEN__))
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#ifndef LOCKMEM
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#define LOCKMEM __attribute__((__used__, __section__ (".lock")))
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#endif
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#ifndef LOCKBITS
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#define LOCKBITS unsigned char __lock LOCKMEM
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#endif
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/* Lock Bit Modes */
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#if defined(__LOCK_BITS_EXIST)
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#define LB_MODE_1 (0xFF)
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#define LB_MODE_2 (0xFE)
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#define LB_MODE_3 (0xFC)
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#endif
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#if defined(__BOOT_LOCK_BITS_0_EXIST)
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#define BLB0_MODE_1 (0xFF)
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#define BLB0_MODE_2 (0xFB)
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#define BLB0_MODE_3 (0xF3)
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#define BLB0_MODE_4 (0xF7)
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#endif
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#if defined(__BOOT_LOCK_BITS_1_EXIST)
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#define BLB1_MODE_1 (0xFF)
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#define BLB1_MODE_2 (0xEF)
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#define BLB1_MODE_3 (0xCF)
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#define BLB1_MODE_4 (0xDF)
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#endif
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#if defined(__BOOT_LOCK_APPLICATION_TABLE_BITS_EXIST)
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#define BLBAT0 ~_BV(2)
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#define BLBAT1 ~_BV(3)
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#endif
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#if defined(__BOOT_LOCK_APPLICATION_BITS_EXIST)
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#define BLBA0 ~_BV(4)
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#define BLBA1 ~_BV(5)
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#endif
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#if defined(__BOOT_LOCK_BOOT_BITS_EXIST)
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#define BLBB0 ~_BV(6)
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#define BLBB1 ~_BV(7)
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#endif
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#define LOCKBITS_DEFAULT (0xFF)
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#endif
/* !(__ASSEMBLER || __DOXYGEN__) */
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#endif
/* _AVR_LOCK_H_ */
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