This chapter documents the Backend for the c16x/st10 microcontroller family.

Note that this module is not yet fully completed!

@section Legal

    This module is copyright in 2002-2004 by Volker Barthelmann.

    This archive may be redistributed without modifications and used
    for non-commercial purposes.

    Distributing modified versions and commercial usage needs my written
    consent.

    Certain modules may fall under additional copyrights.


@section Additional options for this module

This module provides the following additional options:

@table @option

    @item -no-translations
        Do not translate between jump instructions.
        If the offset of a @code{jmpr}
        instruction is too large, it will not be translated to
        @code{jmps} but an error will be emitted.

        Also, @code{jmpa} will not be optimized to @code{jmpr}.

        The pseudo-instruction @code{jmp} will still be translated.

    @item -jmpa
        A @code{jmp} or @code{jmpr} instruction that is translated due to
        its offset being larger than 8 bits will be translated to a
        @code{jmpa} rather than a @code{jmps}, if possible.

@end table

@section General

This backend accepts c16x/st10 instructions as described in the
Infineon instruction set manuals.

The target address type is 32bit.

Default alignment for sections and instructions is 2 bytes.

@section Extensions

This backend provides the following specific extensions:

@itemize @minus

@item
There is a pseudo instruction @code{jmp} that will be translated
        either to a @code{jmpr} or @code{jmpa} instruction, depending on
        the offset.

@item
 The @code{sfr} pseudo opcode can be used to declare special function
        registers. It has two, three of four arguments. The first argument
        is the identifier to be declared as special function register.
        The second argument is either the 16bit sfr address or its 8bit base
        address (0xfe for normal sfrs and
        0xf0 for extended special function registers). In the latter case,
        the third argument is
        the 8bit sfr number. If another argument is given, it specifies the
        bit-number in the sfr (i.e. the declaration declares a single bit).

Example:
@example
.sfr    zeros,0xfe,0x8e
@end example

@item
        @code{SEG} and @code{SOF} can be used to obtain the segment or
        segment offset of a full address.
Example:
@example
        mov r3,#SEG farfunc
@end example

@end itemize

@section Optimizations

This backend performs the following optimizations:

@itemize @minus

@item
 @code{jmp} is translated to @code{jmpr}, if possible. Also, if
        @option{-no-translations} was not specified, @code{jmpr} and
        @code{jmpa} are translated.

@item 
 Relative jump instructions with an offset that does not fit into
        8 bits are translated to a @code{jmps} instruction or an inverted
        jump around a @code{jmps} instruction.

@item
 For instruction that have two forms @code{gpr,#IMM3/4} and
        @code{reg,#IMM16} the smaller form is used, if possible.

@end itemize

@section Known Problems

    Some known problems of this module at the moment:

@itemize @minus

@item Lots...

@end itemize

@section Error Messages

This module has the following error messages:

@itemize @minus
@item 2001: illegal operand
@item 2002: word register expected
@item 2004: value does not find in %d bits
@item 2005: data size not supported
@item 2006: illegal use of SOF
@item 2007: illegal use of SEG
@item 2008: illegal use of DPP prefix
@end itemize
