path: root/gas/doc/c-m68hc11.texi

@c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 2000
@c Free Software Foundation, Inc.
@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
@ifset GENERIC
@page
@node M68HC11-Dependent
@chapter M68HC11 and M68HC12 Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter M68HC11 and M68HC12 Dependent Features
@end ifclear

@cindex M68HC11 and M68HC12 support
@menu
* M68HC11-Opts::                   M68HC11 and M68HC12 Options
* M68HC11-Syntax::                 Syntax
* M68HC11-Float::                  Floating Point
* M68HC11-opcodes::                Opcodes
@end menu

@node M68HC11-Opts
@section M68HC11 and M68HC12 Options

@cindex options, M68HC11
@cindex M68HC11 options
The Motorola 68HC11 and 68HC12 version of @code{@value{AS}} has a few machine
dependent options.

@cindex @samp{-m68hc11}
This option switches the assembler in the M68HC11 mode. In this mode,
the assembler only accepts 68HC11 operands and mnemonics. It produces
code for the 68HC11.

@cindex @samp{-m68hc12}
This option switches the assembler in the M68HC12 mode. In this mode,
the assembler also accepts 68HC12 operands and mnemonics. It produces
code for the 68HC12. A fiew 68HC11 instructions are replaced by
some 68HC12 instructions as recommended by Motorola specifications.

@cindex @samp{--strict-direct-mode}
You can use the @samp{--strict-direct-mode} option to disable
the automatic translation of direct page mode addressing into
extended mode when the instruction does not support direct mode.
For example, the @samp{clr} instruction does not support direct page
mode addressing. When it is used with the direct page mode,
@code{@value{AS}} will ignore it and generate an absolute addressing.
This option prevents @code{@value{AS}} from doing this, and the wrong
usage of the direct page mode will raise an error.

@cindex @samp{--short-branchs}
The @samp{--short-branchs} option turns off the translation of
relative branches into absolute branches when the branch offset is
out of range. By default @code{@value{AS}} transforms the relative
branch (@samp{bsr}, @samp{bgt}, @samp{bge}, @samp{beq}, @samp{bne},
@samp{ble}, @samp{blt}, @samp{bhi}, @samp{bcc}, @samp{bls},
@samp{bcs}, @samp{bmi}, @samp{bvs}, @samp{bvs}, @samp{bra}) into
an absolute branch when the offset is out of the -128 .. 127 range.
In that case, the @samp{bsr} instruction is translated into a
@samp{jsr}, the @samp{bra} instruction is translated into a
@samp{jmp} and the conditional branchs instructions are inverted and
followed by a @samp{jmp}. This option disables these translations
and @code{@value{AS}} will generate an error if a relative branch
is out of range. This option does not affect the optimization
associated to the @samp{jbra}, @samp{jbsr} and @samp{jbXX} pseudo opcodes.

@cindex @samp{--force-long-branchs}
The @samp{--force-long-branchs} option forces the translation of
relative branches into absolute branches. This option does not affect
the optimization associated to the @samp{jbra}, @samp{jbsr} and
@samp{jbXX} pseudo opcodes. 

@cindex @samp{--print-insn-syntax}
You can use the @samp{--print-insn-syntax} option to obtain the
syntax description of the instruction when an error is detected.

@cindex @samp{--print-opcodes}
The @samp{--print-opcodes} option prints the list of all the
instructions with their syntax. The first item of each line
represents the instruction name and the rest of the line indicates
the possible operands for that instruction. The list is printed
in alphabetical order. Once the list is printed @code{@value{AS}}
exits.

@cindex @samp{--generate-example}
The @samp{--generate-example} option is similar to @samp{--print-opcodes}
but it generates an example for each instruction instead.

@node M68HC11-Syntax
@section Syntax

@cindex M68HC11 syntax
@cindex syntax, M68HC11

In the M68HC11 syntax, the instruction name comes first and it may
be followed by one or several operands (up to three). Operands are
separated by comma (@samp{,}). In the normal mode,
@code{@value{AS}} will complain if too many operands are specified for
a given instruction. In the MRI mode (turned on with @samp{-M} option),
it will treat them as comments. Example:

@smallexample
inx
lda  #23
bset 2,x #4
brclr *bot #8 foo
@end smallexample

@cindex M68HC11 addressing modes
@cindex addressing modes, M68HC11
The following addressing modes are understood:
@table @dfn
@item Immediate
@samp{#@var{number}}

@item Address Register
@samp{@var{number},X}, @samp{@var{number},Y}

The @var{number} may be omitted in which case 0 is assumed.

@item Direct Addressing mode
@samp{*@var{symbol}}, or @samp{*@var{digits}}

@item Absolute
@samp{@var{symbol}}, or @samp{@var{digits}}
@end table

@node M68HC11-Float
@section Floating Point

@cindex floating point, M68HC11
@cindex M68HC11 floating point
Packed decimal (P) format floating literals are not supported.
Feel free to add the code!

The floating point formats generated by directives are these.

@table @code
@cindex @code{float} directive, M68HC11
@item .float
@code{Single} precision floating point constants.

@cindex @code{double} directive, M68HC11
@item .double
@code{Double} precision floating point constants.

@cindex @code{extend} directive M68HC11
@cindex @code{ldouble} directive M68HC11
@item .extend
@itemx .ldouble
@code{Extended} precision (@code{long double}) floating point constants.
@end table

@need 2000
@node M68HC11-opcodes
@section Opcodes

@cindex M68HC11 opcodes
@cindex opcodes, M68HC11
@cindex instruction set, M68HC11

@menu
* M68HC11-Branch::                 Branch Improvement
@end menu

@node M68HC11-Branch
@subsection Branch Improvement

@cindex pseudo-opcodes, M68HC11
@cindex M68HC11 pseudo-opcodes
@cindex branch improvement, M68HC11
@cindex M68HC11 branch improvement

Certain pseudo opcodes are permitted for branch instructions.
They expand to the shortest branch instruction that reach the
target. Generally these mnemonics are made by prepending @samp{j} to
the start of Motorola mnemonic. These pseudo opcodes are not affected
by the @samp{--short-branchs} or @samp{--force-long-branchs} options.

The following table summarizes the pseudo-operations.

@smallexample
                              Displacement Width
          +-------------------------------------------------------------+
          |                     Options                                 |
          |    --short-branchs            --force-long-branchs          |
          +--------------------------+----------------------------------+
Pseudo-Op |BYTE             WORD     | BYTE          WORD               |
          +--------------------------+----------------------------------+
      bsr | bsr <pc-rel>    <error>  |               jsr <abs>          |
      bra | bra <pc-rel>    <error>  |               jmp <abs>          |
     jbsr | bsr <pc-rel>   jsr <abs> | bsr <pc-rel>  jsr <abs>          |
     jbra | bra <pc-rel>   jmp <abs> | bra <pc-rel>  jmp <abs>          |
      bXX | bXX <pc-rel>    <error>  |               bNX +3; jmp <abs>  | 
     jbXX | bXX <pc-rel>   bNX +3;   | bXX <pc-rel>  bNX +3; jmp <abs>  |
          |                jmp <abs> |                                  |
          +--------------------------+----------------------------------+
XX: condition
NX: negative of condition XX

@end smallexample

@table @code
@item jbsr
@itemx jbra
These are the simplest jump pseudo-operations; they always map to one
particular machine instruction, depending on the displacement to the
branch target.

@item jb@var{XX}
Here, @samp{jb@var{XX}} stands for an entire family of pseudo-operations,
where @var{XX} is a conditional branch or condition-code test.  The full
list of pseudo-ops in this family is:
@smallexample
 jbcc   jbeq   jbge   jbgt   jbhi   jbvs   jbpl  jblo
 jbcs   jbne   jblt   jble   jbls   jbvc   jbmi
@end smallexample

For the cases of non-PC relative displacements and long displacements,
@code{@value{AS}} issues a longer code fragment in terms of
@var{NX}, the opposite condition to @var{XX}.  For example, for the
non-PC relative case:
@smallexample
    jb@var{XX} foo
@end smallexample
gives
@smallexample
     b@var{NX}s oof
     jmp foo
 oof:
@end smallexample

@end table