sfr_defs.h

/* Copyright (c) 2002, Marek Michalkiewicz <marekm@amelek.gda.pl>

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
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* Redistributions in binary form must reproduce the above copyright
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the documentation and/or other materials provided with the
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* Neither the name of the copyright holders nor the names of
contributors may be used to endorse or promote products derived
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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
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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.  */

/* avr/sfr_defs.h - macros for accessing AVR special function registers */

/* $Id$ */

#ifndef _AVR_SFR_DEFS_H_
#define _AVR_SFR_DEFS_H_ 1

/** \defgroup avr_sfr_notes Additional notes from <avr/sfr_defs.h>
\ingroup avr_sfr

The \c <avr/sfr_defs.h> file is included by all of the \c <avr/ioXXXX.h>
files, which use macros defined here to make the special function register
definitions look like C variables or simple constants, depending on the
<tt>_SFR_ASM_COMPAT</tt> define.  Some examples from \c <avr/iocanxx.h> to
show how to define such macros:

\code
#define PORTA   _SFR_IO8(0x02)
#define EEAR    _SFR_IO16(0x21)
#define UDR0    _SFR_MEM8(0xC6)
#define TCNT3   _SFR_MEM16(0x94)
#define CANIDT  _SFR_MEM32(0xF0)
\endcode

If \c _SFR_ASM_COMPAT is not defined, C programs can use names like
<tt>PORTA</tt> directly in C expressions (also on the left side of
assignment operators) and GCC will do the right thing (use short I/O
instructions if possible).  The \c __SFR_OFFSET definition is not used in
any way in this case.

Define \c _SFR_ASM_COMPAT as 1 to make these names work as simple constants
(addresses of the I/O registers).  This is necessary when included in
preprocessed assembler (*.S) source files, so it is done automatically if
\c __ASSEMBLER__ is defined.  By default, all addresses are defined as if
they were memory addresses (used in \c lds/sts instructions).  To use these
addresses in \c in/out instructions, you must subtract 0x20 from them.

For more backwards compatibility, insert the following at the start of your
old assembler source file:

\code
#define __SFR_OFFSET 0
\endcode

This automatically subtracts 0x20 from I/O space addresses, but it's a
hack, so it is recommended to change your source: wrap such addresses in
macros defined here, as shown below.  After this is done, the
<tt>__SFR_OFFSET</tt> definition is no longer necessary and can be removed.

Real example - this code could be used in a boot loader that is portable
between devices with \c SPMCR at different addresses.

\verbatim
<avr/iom163.h>: #define SPMCR _SFR_IO8(0x37)
<avr/iom128.h>: #define SPMCR _SFR_MEM8(0x68)
\endverbatim

\code
#if _SFR_IO_REG_P(SPMCR)
#else
#endif
\endcode

You can use the \c in/out/cbi/sbi/sbic/sbis instructions, without the
<tt>_SFR_IO_REG_P</tt> test, if you know that the register is in the I/O
space (as with \c SREG, for example).  If it isn't, the assembler will
complain (I/O address out of range 0...0x3f), so this should be fairly
safe.

If you do not define \c __SFR_OFFSET (so it will be 0x20 by default), all
special register addresses are defined as memory addresses (so \c SREG is
0x5f), and (if code size and speed are not important, and you don't like
the ugly \#if above) you can always use lds/sts to access them.  But, this
will not work if <tt>__SFR_OFFSET</tt> != 0x20, so use a different macro
(defined only if <tt>__SFR_OFFSET</tt> == 0x20) for safety:

\code
\endcode

In C programs, all 3 combinations of \c _SFR_ASM_COMPAT and
<tt>__SFR_OFFSET</tt> are supported - the \c _SFR_ADDR(SPMCR) macro can be
used to get the address of the \c SPMCR register (0x57 or 0x68 depending on
device). */

#ifdef __ASSEMBLER__
#define _SFR_ASM_COMPAT 1
#elif !defined(_SFR_ASM_COMPAT)
#define _SFR_ASM_COMPAT 0
#endif

#ifndef __ASSEMBLER__
/* These only work in C programs.  */
#include <inttypes.h>

#endif

#if _SFR_ASM_COMPAT

#ifndef __SFR_OFFSET
/* Define as 0 before including this file for compatibility with old asm
sources that don't subtract __SFR_OFFSET from symbolic I/O addresses.  */
#  if __AVR_ARCH__ >= 100
#    define __SFR_OFFSET 0x00
#  else
#    define __SFR_OFFSET 0x20
#  endif
#endif

#if (__SFR_OFFSET != 0) && (__SFR_OFFSET != 0x20)
#error "__SFR_OFFSET must be 0 or 0x20"
#endif

#define _SFR_IO_REG_P(sfr) ((sfr) < 0x40 + __SFR_OFFSET)

#if (__SFR_OFFSET == 0x20)
/* No need to use ?: operator, so works in assembler too.  */
#elif !defined(__ASSEMBLER__)
#endif

#else  /* !_SFR_ASM_COMPAT */

#ifndef __SFR_OFFSET
#  if __AVR_ARCH__ >= 100
#    define __SFR_OFFSET 0x00
#  else
#    define __SFR_OFFSET 0x20
#  endif
#endif

#define _SFR_IO_REG_P(sfr) (_SFR_MEM_ADDR(sfr) < 0x40 + __SFR_OFFSET)

#endif /* !_SFR_ASM_COMPAT */

/** \name Bit manipulation */

/*@{*/
/** \def _BV
\ingroup avr_sfr

\code #include <avr/io.h>\endcode

Converts a bit number into a byte value.

\note The bit shift is performed by the compiler which then inserts the
result into the code. Thus, there is no run-time overhead when using
_BV(). */

#define _BV(bit) (1 << (bit))

/*@}*/

#ifndef _VECTOR
#define _VECTOR(N) __vector_ ## N
#endif

#ifndef __ASSEMBLER__

/** \name IO register bit manipulation */

/*@{*/

/** \def bit_is_set
\ingroup avr_sfr

\code #include <avr/io.h>\endcode

Test whether bit \c bit in IO register \c sfr is set.
This will return a 0 if the bit is clear, and non-zero
if the bit is set. */

#define bit_is_set(sfr, bit) (_SFR_BYTE(sfr) & _BV(bit))

/** \def bit_is_clear
\ingroup avr_sfr

\code #include <avr/io.h>\endcode

Test whether bit \c bit in IO register \c sfr is clear.
This will return non-zero if the bit is clear, and a 0
if the bit is set. */

#define bit_is_clear(sfr, bit) (!(_SFR_BYTE(sfr) & _BV(bit)))

/** \def loop_until_bit_is_set
\ingroup avr_sfr

\code #include <avr/io.h>\endcode

Wait until bit \c bit in IO register \c sfr is set. */

#define loop_until_bit_is_set(sfr, bit) do { } while (bit_is_clear(sfr, bit))

/** \def loop_until_bit_is_clear
\ingroup avr_sfr

\code #include <avr/io.h>\endcode

Wait until bit \c bit in IO register \c sfr is clear. */

#define loop_until_bit_is_clear(sfr, bit) do { } while (bit_is_set(sfr, bit))

/*@}*/

#endif /* !__ASSEMBLER__ */

#endif  /* _SFR_DEFS_H_ */