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