gas/doc/c-z80.texi

   1 @c This is part of the GAS manual.
   2 @c For copying conditions, see the file as.texinfo.
   3
   4 @ifset GENERIC
   5 @page
   6 @node Z80-Dependent
   7 @chapter Z80 Dependent Features
   8 @end ifset
   9
  10 @c DO-NOT-COMMIT
  11
  12 @ifclear GENERIC
  13 @node Machine Dependencies
  14 @chapter Z80 Dependent Features
  15 @end ifclear
  16
  17 @cindex Z80 support
  18 @menu
  19 * Z80 Options::              Options
  20 * Z80 Syntax::               Syntax
  21 * Z80 Floating Point::       Floating Point
  22 * Z80 Directives::           Z80 Machine Directives
  23 * Z80 Opcodes::              Opcodes
  24 @end menu
  25
  26 @node Z80 Options
  27 @section Options
  28 @cindex Z80 options
  29 @cindex options for Z80
  30 The Zilog Z80 and Ascii R800 version of @code{@value{AS}} have a few machine
  31 dependent options.
  32 @table @option
  33 @cindex @code{-z80} command line option, Z80
  34 @item -z80
  35 Produce code for the Z80 processor. There are additional options to
  36 request warnings and error messages for undocumented instructions.
  37 @item  -ignore-undocumented-instructions
  38 @itemx -Wnud
  39 Silently assemble undocumented Z80-instructions that have been adopted
  40 as documented R800-instructions.
  41 @item  -ignore-unportable-instructions
  42 @itemx -Wnup
  43 Silently assemble all undocumented Z80-instructions.
  44 @item  -warn-undocumented-instructions
  45 @itemx -Wud
  46 Issue warnings for undocumented Z80-instructions that work on R800, do
  47 not assemble other undocumented instructions without warning.
  48 @item  -warn-unportable-instructions
  49 @itemx -Wup
  50 Issue warnings for other undocumented Z80-instructions, do not treat any
  51 undocumented instructions as errors.
  52 @item  -forbid-undocumented-instructions
  53 @itemx -Fud
  54 Treat all undocumented z80-instructions as errors.
  55 @item  -forbid-unportable-instructions
  56 @itemx -Fup
  57 Treat undocumented z80-instructions that do not work on R800 as errors.
  58
  59 @cindex @code{-r800} command line option, Z80
  60 @item -r800
  61 Produce code for the R800 processor. The assembler does not support
  62 undocumented instructions for the R800.
  63 In line with common practice, @code{@value{AS}} uses Z80 instriction names
  64 for the R800 processor, as far as they exist.
  65 @end table
  66
  67 @cindex Z80 Syntax
  68 @node Z80 Syntax
  69 @section Syntax
  70 The assembler syntax closely follows the 'Z80 family CPU User Manual' by
  71 Zilog.
  72 In expressions a single @samp{=} may be used as ``is equal to''
  73 comparison operator.
  74
  75 Suffices can be used to indicate the radix of integer constants;
  76 @samp{H} or @samp{h} for hexadecimal, @samp{D} or @samp{d} for decimal,
  77 @samp{Q}, @samp{O}, @samp{q} or @samp{o} for octal, and @samp{B} for
  78 binary.
  79
  80 The suffix @samp{b} denotes a backreference to local label.
  81
  82 @menu
  83 * Z80-Chars::                Special Characters
  84 * Z80-Regs::                 Register Names
  85 * Z80-Case::                 Case Sensitivity
  86 @end menu
  87
  88 @node Z80-Chars
  89 @subsection Special Characters
  90
  91 @cindex line comment character, Z80
  92 @cindex Z80 line comment character
  93 The semicolon @samp{;} is the line comment character;
  94
  95 @cindex location counter, Z80
  96 @cindex hexadecimal prefix, Z80
  97 @cindex Z80 $
  98 The dollar sign @samp{$} can be used as a prefix for hexadecimal numbers
  99 and as a symbol denoting the current location counter.
 100
 101 @cindex character escapes, Z80
 102 @cindex Z80, \
 103 A backslash @samp{\} is an ordinary character for the Z80 assembler.
 104
 105 @cindex character constant, Z80
 106 @cindex single quote, Z80
 107 @cindex Z80 '
 108 The single quote @samp{'} must be followed by a closing quote. If there
 109 is one character inbetween, it is a character constant, otherwise it is
 110 a string constant.
 111
 112 @node Z80-Regs
 113 @subsection Register Names
 114 @cindex Z80 registers
 115 @cindex register names, Z80
 116
 117 The registers are referred to with the letters assigned to them by
 118 Zilog. In addition @command{@value{AS}} recognises @samp{ixl} and
 119 @samp{ixh} as the least and most significant octet in @samp{ix}, and
 120 similarly @samp{iyl} and  @samp{iyh} as parts of @samp{iy}.
 121
 122 @c The @samp{'} in @samp{ex af,af'} may be omitted.
 123
 124 @node Z80-Case
 125 @subsection Case Sensitivity
 126 @cindex Z80, case sensitivity
 127 @cindex case sensitivity, Z80
 128
 129 Upper and lower case are equivalent in register names, opcodes,
 130 condition codes  and assembler directives.
 131 The case of letters is significant in labels and symbol names. The case
 132 is also important to distinguish the suffix @samp{b} for a backward reference
 133 to a local label from the suffix @samp{B} for a number in binary notation.
 134
 135 @node Z80 Floating Point
 136 @section Floating Point
 137 @cindex floating point, Z80
 138 @cindex Z80 floating point
 139 Floating-point numbers are not supported.
 140
 141 @node Z80 Directives
 142 @section Z80 Assembler Directives
 143
 144 @command{@value{AS}} for the Z80 supports some additional directives for
 145 compatibility with other assemblers.
 146
 147 @cindex Z80-only directives
 148 These are the additional directives in @code{@value{AS}} for the Z80:
 149
 150 @table @code
 151 @item db @var{expression}|@var{string}[,@var{expression}|@var{string}...]
 152 @itemx defb @var{expression}|@var{string}[,@var{expression}|@var{string}...]
 153 For each @var{string} the characters are copied to the object file, for
 154 each other @var{expression} the value is stored in one byte, ignoring
 155 overflow.
 156
 157 @item dw @var{expression}[,@var{expression}...]
 158 @itemx defw @var{expression}[,@var{expression}...]
 159 For each @var{expression} the value is stored in two bytes, ignoring
 160 overflow.
 161
 162 @item ds @var{count}[, @var{value}]
 163 @itemx defs @var{count}[, @var{value}]
 164 @c Synonyms for @code{ds.b},
 165 @c which should have been described elsewhre
 166 Fill @var{count} bytes in the object file with @var{value}, if
 167 @var{value} is omitted it defaults to zero.
 168
 169 @item @var{symbol} equ @var{expression}
 170 @itemx @var{symbol} defl @var{expression}
 171 These directives set the value of @var{symbol} to @var{expression}.  To
 172 keep code portable to other assemblers it is best to use @samp{equ} for
 173 the first definition and @samp{defl} for redefinitions.
 174
 175 @item set
 176 This is a normal instruction on Z80, and not an assembler directive.
 177
 178 @item psect @var{name}
 179 A synonym for @xref{Section}, no second argument should be given.
 180 @ignore
 181
 182 The following attributes will possibly be recognised in the future
 183 @table @code
 184 @item abs
 185 The section is to be absolute. @code{@value{AS}} will issue an error
 186 message because it can not produce an absolute section.
 187 @item global
 188 The section is to be concatenated with other sections of the same name
 189 by the linker, this is the default.
 190 @item local
 191 The section is not global. @code{@value{AS}} will issue a warning if
 192 object file format is not soff.
 193 @item ovrld
 194 The section is to be overlapped with other sections of the same name by
 195 the linker. @code{@value{AS}} will issue an error message
 196 because it can not mark a section as such.
 197 @item pure
 198 The section is marked as read only.
 199 @end table
 200 @end ignore
 201
 202 @end table
 203
 204 @node Z80 Opcodes
 205 @section Opcodes
 206 In line with commmon practice Z80 mnonics are used for both the Z80 and
 207 the R800.
 208
 209 In many instructions it is possible to use one of the half index
 210 registers (@samp{ixl},@samp{ixh},@samp{iyl},@samp{iyh}) in stead of an
 211 8-bit general purpose register. This yields instructions that are
 212 documented on the R800 and undocumented on the Z80.
 213 Similarly @code{in f,(c)} is documented on the R800 and undocumented on
 214 the Z80.
 215
 216 The assembler also supports the following undocumented Z80-instructions,
 217 that have not been adopted in the R800 instruction set:
 218 @table @code
 219 @item out (c),0
 220 Sends zero to the port pointed to by register c.
 221
 222 @item sli @var{m}
 223 Equivalent to @code{@var{m} = (@var{m}<<1)+1}, the operand @var{m} can
 224 be any operand that is valid for @samp{sla}. One can use @samp{sll} as a
 225 synonym for @samp{sli}.
 226
 227 @item @var{op} (ix+@var{d}), @var{r}
 228 This is equivalent to
 229
 230 @example
 231 ld @var{r}, (ix+@var{d})
 232 @var{opc} @var{r}
 233 ld (ix+@var{d}), @var{r}
 234 @end example
 235
 236 The operation @samp{@var{opc}} may be any of @samp{res @var{b},},
 237 @samp{set @var{b},}, @samp{rl}, @samp{rlc}, @samp{rr}, @samp{rrc},
 238 @samp{sla}, @samp{sli}, @samp{sra} and @samp{srl}, and the register
 239 @samp{@var{r}} may be any of @samp{a}, @samp{b}, @samp{c}, @samp{d},
 240 @samp{e}, @samp{h} and @samp{l}.
 241
 242 @item @var{opc} (iy+@var{d}), @var{r}
 243 As above, but with @samp{iy} instead of @samp{ix}.
 244 @end table
 245
 246 The web site at @uref{http://www.z80.info} is a good starting place to
 247 find more information on programming the Z80.
 248