# cpufunc.h

/* Copyright (c) 2010, Joerg Wunsch

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/cpufunc.h - Special CPU functions */

#ifndef _AVR_CPUFUNC_H_
#define _AVR_CPUFUNC_H_ 1

/** \file */
/** \defgroup avr_cpufunc <avr/cpufunc.h>: Special AVR CPU functions
\code #include <avr/cpufunc.h> \endcode

This header file contains macros that access special functions of
the AVR CPU which do not fit into any of the other header files.

*/

#if defined(__DOXYGEN__)
/**
\ingroup avr_cpufunc
\def _NOP

Execute a <i>no operation</i> (NOP) CPU instruction.  This
should not be used to implement delays, better use the functions
from <util/delay_basic.h> or <util/delay.h> for this.  For
debugging purposes, a NOP can be useful to have an instruction that
is guaranteed to be not optimized away by the compiler, so it can
always become a breakpoint in the debugger.
*/
#define _NOP()
#else  /* real code */
#define _NOP() __asm__ __volatile__("nop")
#endif  /* __DOXYGEN__ */

#if defined(__DOXYGEN__)
/**
\ingroup avr_cpufunc
\def _MemoryBarrier

Implement a read/write <i>memory barrier</i>.  A memory
barrier instructs the compiler to not cache any memory data in
registers beyond the barrier.  This can sometimes be more effective
than blocking certain optimizations by declaring some object with a
\c volatile qualifier.

See \ref optim_code_reorder for things to be taken into account
with respect to compiler optimizations.
*/
#define _MemoryBarrier()
#else  /* real code */
#define _MemoryBarrier() __asm__ __volatile__("":::"memory")
#endif  /* __DOXYGEN__ */

#endif /* _AVR_CPUFUNC_H_ */