| AVR Libc Home Page |
|
AVR Libc Development Pages | ||
| Main Page | User Manual | Reference | FAQ | Example Projects |
cpufunc.8h
Go to the documentation of this file.
01 Copyright (c) 2010, Joerg Wunsch02 All rights reserved. 03 3 04 4Redistribution and use in source and binary forms, with or without 05 5modification, are permitted provided that the following conditions are met: 06 607 7* Redistributions of source code must retain the above copyright 08 8notice, this list of conditions and the following disclaimer. 09 910 10* Redistributions in binary form must reproduce the above copyright 11 11notice, this list of conditions and the following disclaimer in 12 12the documentation and/or other materials provided with the 13 13distribution. 14 1415 15* Neither the name of the copyright holders nor the names of 16 16contributors may be used to endorse or promote products derived 17 17from this software without specific prior written permission. 18 1819 19THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 20 20AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 21 21IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 22 22ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 23 23LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 24CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 25SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 26INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 27CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 28ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 29POSSIBILITY OF SUCH DAMAGE. */ 30 3031 31/* $Id: cpufunc.h 2307 2013-01-26 22:39:58Z dmix $ */ 32 3233 33/* avr/cpufunc.h - Special CPU functions */ 34 3435 35#ifndef _AVR_CPUFUNC_H_ 36 36#define _AVR_CPUFUNC_H_ 1 37 3738 38/** \file */ 39 39/** \defgroup avr_cpufunc <avr/cpufunc.h>: Special AVR CPU functions 40 40\code #include <avr/cpufunc.h> \endcode 41 4142 42This header file contains macros that access special functions of 43 43the AVR CPU which do not fit into any of the other header files. 44 4445 45*/ 46 4647 47#if defined(__DOXYGEN__) 48 48/** 49 49\ingroup avr_cpufunc 50 50\def _NOP 51 5152 52Execute a <i>no operation</i> (NOP) CPU instruction. This 53 53should not be used to implement delays, better use the functions 54 54from <util/delay_basic.h> or <util/delay.h> for this. For 55 55debugging purposes, a NOP can be useful to have an instruction that 56 56is guaranteed to be not optimized away by the compiler, so it can 57 57always become a breakpoint in the debugger. 58 58*/ 59 59#define _NOP() 60 60#else /* real code */ 61 61#define _NOP() __asm__ __volatile__("nop") 62 62#endif /* __DOXYGEN__ */ 63 6364 64#if defined(__DOXYGEN__) 65 65/** 66 66\ingroup avr_cpufunc 67 67\def _MemoryBarrier 68 6869 69Implement a read/write <i>memory barrier</i>. A memory 70 70barrier instructs the compiler to not cache any memory data in 71 71registers beyond the barrier. This can sometimes be more effective 72 72than blocking certain optimizations by declaring some object with a 73 73\c volatile qualifier. 74 7475 75See \ref optim_code_reorder for things to be taken into account 76 76with respect to compiler optimizations. 77 77*/ 78 78#define _MemoryBarrier() 79 79#else /* real code */ 80 80#define _MemoryBarrier() __asm__ __volatile__("":::"memory") 81 81#endif /* __DOXYGEN__ */ 82 8283 83#endif /* _AVR_CPUFUNC_H_ */