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| <title>Using as: Z80 Opcodes</title> |
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| <a name="Opcodes-18"></a> |
| <h4 class="subsection">9.46.5 Opcodes</h4> |
| <p>In line with common practice, Z80 mnemonics are used for both the Z80 and |
| the R800. |
| </p> |
| <p>In many instructions it is possible to use one of the half index |
| registers (‘<samp>ixl</samp>’,‘<samp>ixh</samp>’,‘<samp>iyl</samp>’,‘<samp>iyh</samp>’) 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)</code> is documented on the R800 and undocumented on |
| the Z80. |
| </p> |
| <p>The assembler also supports the following undocumented Z80-instructions, |
| that have not been adopted in the R800 instruction set: |
| </p><dl compact="compact"> |
| <dt><code>out (c),0</code></dt> |
| <dd><p>Sends zero to the port pointed to by register c. |
| </p> |
| </dd> |
| <dt><code>sli <var>m</var></code></dt> |
| <dd><p>Equivalent to <code><var>m</var> = (<var>m</var><<1)+1</code>, the operand <var>m</var> can |
| be any operand that is valid for ‘<samp>sla</samp>’. One can use ‘<samp>sll</samp>’ as a |
| synonym for ‘<samp>sli</samp>’. |
| </p> |
| </dd> |
| <dt><code><var>op</var> (ix+<var>d</var>), <var>r</var></code></dt> |
| <dd><p>This is equivalent to |
| </p> |
| <div class="example"> |
| <pre class="example">ld <var>r</var>, (ix+<var>d</var>) |
| <var>opc</var> <var>r</var> |
| ld (ix+<var>d</var>), <var>r</var> |
| </pre></div> |
| |
| <p>The operation ‘<samp><var>opc</var></samp>’ may be any of ‘<samp>res <var>b</var>,</samp>’, |
| ‘<samp>set <var>b</var>,</samp>’, ‘<samp>rl</samp>’, ‘<samp>rlc</samp>’, ‘<samp>rr</samp>’, ‘<samp>rrc</samp>’, |
| ‘<samp>sla</samp>’, ‘<samp>sli</samp>’, ‘<samp>sra</samp>’ and ‘<samp>srl</samp>’, and the register |
| ‘<samp><var>r</var></samp>’ may be any of ‘<samp>a</samp>’, ‘<samp>b</samp>’, ‘<samp>c</samp>’, ‘<samp>d</samp>’, |
| ‘<samp>e</samp>’, ‘<samp>h</samp>’ and ‘<samp>l</samp>’. |
| </p> |
| </dd> |
| <dt><code><var>opc</var> (iy+<var>d</var>), <var>r</var></code></dt> |
| <dd><p>As above, but with ‘<samp>iy</samp>’ instead of ‘<samp>ix</samp>’. |
| </p></dd> |
| </dl> |
| |
| <p>The web site at <a href="http://www.z80.info">http://www.z80.info</a> is a good starting place to |
| find more information on programming the Z80. |
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