Retro68/binutils/gas/doc/c-z80.texi

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@c Copyright (C) 2011-2017 Free Software Foundation, Inc.
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@c This is part of the GAS manual.
@c For copying conditions, see the file as.texinfo.
@ifset GENERIC
@page
@node Z80-Dependent
@chapter Z80 Dependent Features
@end ifset
@ifclear GENERIC
@node Machine Dependencies
@chapter Z80 Dependent Features
@end ifclear
@cindex Z80 support
@menu
* Z80 Options:: Options
* Z80 Syntax:: Syntax
* Z80 Floating Point:: Floating Point
* Z80 Directives:: Z80 Machine Directives
* Z80 Opcodes:: Opcodes
@end menu
@node Z80 Options
@section Options
@cindex Z80 options
@cindex options for Z80
The Zilog Z80 and Ascii R800 version of @code{@value{AS}} have a few machine
dependent options.
@table @option
@cindex @code{-z80} command line option, Z80
@item -z80
Produce code for the Z80 processor. There are additional options to
request warnings and error messages for undocumented instructions.
@item -ignore-undocumented-instructions
@itemx -Wnud
Silently assemble undocumented Z80-instructions that have been adopted
as documented R800-instructions.
@item -ignore-unportable-instructions
@itemx -Wnup
Silently assemble all undocumented Z80-instructions.
@item -warn-undocumented-instructions
@itemx -Wud
Issue warnings for undocumented Z80-instructions that work on R800, do
not assemble other undocumented instructions without warning.
@item -warn-unportable-instructions
@itemx -Wup
Issue warnings for other undocumented Z80-instructions, do not treat any
undocumented instructions as errors.
@item -forbid-undocumented-instructions
@itemx -Fud
Treat all undocumented z80-instructions as errors.
@item -forbid-unportable-instructions
@itemx -Fup
Treat undocumented z80-instructions that do not work on R800 as errors.
@cindex @code{-r800} command line option, Z80
@item -r800
Produce code for the R800 processor. The assembler does not support
undocumented instructions for the R800.
In line with common practice, @code{@value{AS}} uses Z80 instruction names
for the R800 processor, as far as they exist.
@end table
@cindex Z80 Syntax
@node Z80 Syntax
@section Syntax
The assembler syntax closely follows the 'Z80 family CPU User Manual' by
Zilog.
In expressions a single @samp{=} may be used as ``is equal to''
comparison operator.
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Suffices can be used to indicate the radix of integer constants;
@samp{H} or @samp{h} for hexadecimal, @samp{D} or @samp{d} for decimal,
@samp{Q}, @samp{O}, @samp{q} or @samp{o} for octal, and @samp{B} for
binary.
The suffix @samp{b} denotes a backreference to local label.
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@menu
* Z80-Chars:: Special Characters
* Z80-Regs:: Register Names
* Z80-Case:: Case Sensitivity
@end menu
@node Z80-Chars
@subsection Special Characters
@cindex line comment character, Z80
@cindex Z80 line comment character
The semicolon @samp{;} is the line comment character;
If a @samp{#} appears as the first character of a line then the whole
line is treated as a comment, but in this case the line could also be
a logical line number directive (@pxref{Comments}) or a preprocessor
control command (@pxref{Preprocessing}).
@cindex line separator, Z80
@cindex statement separator, Z80
@cindex Z80 line separator
The Z80 assembler does not support a line separator character.
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@cindex location counter, Z80
@cindex hexadecimal prefix, Z80
@cindex Z80 $
The dollar sign @samp{$} can be used as a prefix for hexadecimal numbers
and as a symbol denoting the current location counter.
@cindex character escapes, Z80
@cindex Z80, \
A backslash @samp{\} is an ordinary character for the Z80 assembler.
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@cindex character constant, Z80
@cindex single quote, Z80
@cindex Z80 '
The single quote @samp{'} must be followed by a closing quote. If there
is one character in between, it is a character constant, otherwise it is
a string constant.
@node Z80-Regs
@subsection Register Names
@cindex Z80 registers
@cindex register names, Z80
The registers are referred to with the letters assigned to them by
Zilog. In addition @command{@value{AS}} recognizes @samp{ixl} and
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@samp{ixh} as the least and most significant octet in @samp{ix}, and
similarly @samp{iyl} and @samp{iyh} as parts of @samp{iy}.
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@c The @samp{'} in @samp{ex af,af'} may be omitted.
@node Z80-Case
@subsection Case Sensitivity
@cindex Z80, case sensitivity
@cindex case sensitivity, Z80
Upper and lower case are equivalent in register names, opcodes,
condition codes and assembler directives.
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The case of letters is significant in labels and symbol names. The case
is also important to distinguish the suffix @samp{b} for a backward reference
to a local label from the suffix @samp{B} for a number in binary notation.
@node Z80 Floating Point
@section Floating Point
@cindex floating point, Z80
@cindex Z80 floating point
Floating-point numbers are not supported.
@node Z80 Directives
@section Z80 Assembler Directives
@command{@value{AS}} for the Z80 supports some additional directives for
compatibility with other assemblers.
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@cindex Z80-only directives
These are the additional directives in @code{@value{AS}} for the Z80:
@table @code
@item db @var{expression}|@var{string}[,@var{expression}|@var{string}...]
@itemx defb @var{expression}|@var{string}[,@var{expression}|@var{string}...]
For each @var{string} the characters are copied to the object file, for
each other @var{expression} the value is stored in one byte.
A warning is issued in case of an overflow.
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@item dw @var{expression}[,@var{expression}...]
@itemx defw @var{expression}[,@var{expression}...]
For each @var{expression} the value is stored in two bytes, ignoring
overflow.
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@item d24 @var{expression}[,@var{expression}...]
@itemx def24 @var{expression}[,@var{expression}...]
For each @var{expression} the value is stored in three bytes, ignoring
overflow.
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@item d32 @var{expression}[,@var{expression}...]
@itemx def32 @var{expression}[,@var{expression}...]
For each @var{expression} the value is stored in four bytes, ignoring
overflow.
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@item ds @var{count}[, @var{value}]
@itemx defs @var{count}[, @var{value}]
@c Synonyms for @code{ds.b},
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@c which should have been described elsewhere
Fill @var{count} bytes in the object file with @var{value}, if
@var{value} is omitted it defaults to zero.
@item @var{symbol} equ @var{expression}
@itemx @var{symbol} defl @var{expression}
These directives set the value of @var{symbol} to @var{expression}. If
@code{equ} is used, it is an error if @var{symbol} is already defined.
Symbols defined with @code{equ} are not protected from redefinition.
@item set
This is a normal instruction on Z80, and not an assembler directive.
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@item psect @var{name}
A synonym for @xref{Section}, no second argument should be given.
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@ignore
The following attributes will possibly be recognized in the future
@table @code
@item abs
The section is to be absolute. @code{@value{AS}} will issue an error
message because it can not produce an absolute section.
@item global
The section is to be concatenated with other sections of the same name
by the linker, this is the default.
@item local
The section is not global. @code{@value{AS}} will issue a warning if
object file format is not soff.
@item ovrld
The section is to be overlapped with other sections of the same name by
the linker. @code{@value{AS}} will issue an error message
because it can not mark a section as such.
@item pure
The section is marked as read only.
@end table
@end ignore
@end table
@node Z80 Opcodes
@section Opcodes
In line with common practice, Z80 mnemonics are used for both the Z80 and
the R800.
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In many instructions it is possible to use one of the half index
registers (@samp{ixl},@samp{ixh},@samp{iyl},@samp{iyh}) in stead of an
8-bit general purpose register. This yields instructions that are
documented on the R800 and undocumented on the Z80.
Similarly @code{in f,(c)} is documented on the R800 and undocumented on
the Z80.
The assembler also supports the following undocumented Z80-instructions,
that have not been adopted in the R800 instruction set:
@table @code
@item out (c),0
Sends zero to the port pointed to by register c.
@item sli @var{m}
Equivalent to @code{@var{m} = (@var{m}<<1)+1}, the operand @var{m} can
be any operand that is valid for @samp{sla}. One can use @samp{sll} as a
synonym for @samp{sli}.
@item @var{op} (ix+@var{d}), @var{r}
This is equivalent to
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@example
ld @var{r}, (ix+@var{d})
@var{opc} @var{r}
ld (ix+@var{d}), @var{r}
@end example
The operation @samp{@var{opc}} may be any of @samp{res @var{b},},
@samp{set @var{b},}, @samp{rl}, @samp{rlc}, @samp{rr}, @samp{rrc},
@samp{sla}, @samp{sli}, @samp{sra} and @samp{srl}, and the register
@samp{@var{r}} may be any of @samp{a}, @samp{b}, @samp{c}, @samp{d},
@samp{e}, @samp{h} and @samp{l}.
@item @var{opc} (iy+@var{d}), @var{r}
As above, but with @samp{iy} instead of @samp{ix}.
@end table
The web site at @uref{http://www.z80.info} is a good starting place to
find more information on programming the Z80.