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<h4 class="subsection">9.53.5 Opcodes</h4>
<p>In line with common practice, Z80 mnemonics are used for both the Z80 and
the R800.
<p>In many instructions it is possible to use one of the half index
registers (‘<samp><span class="samp">ixl</span></samp>’,‘<samp><span class="samp">ixh</span></samp>’,‘<samp><span class="samp">iyl</span></samp>’,‘<samp><span class="samp">iyh</span></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>The assembler also supports the following undocumented Z80-instructions,
that have not been adopted in the R800 instruction set:
<dl>
<dt><code>out (c),0</code><dd>Sends zero to the port pointed to by register c.
<br><dt><code>sli </code><var>m</var><dd>Equivalent to <var>m</var><code> = (</code><var>m</var><code><<1)+1</code>, the operand <var>m</var> can
be any operand that is valid for ‘<samp><span class="samp">sla</span></samp>’. One can use ‘<samp><span class="samp">sll</span></samp>’ as a
synonym for ‘<samp><span class="samp">sli</span></samp>’.
<br><dt><var>op</var><code> (ix+</code><var>d</var><code>), </code><var>r</var><dd>This is equivalent to
<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>
<p>The operation ‘<samp><var>opc</var></samp>’ may be any of ‘<samp><span class="samp">res </span><var>b</var><span class="samp">,</span></samp>’,
‘<samp><span class="samp">set </span><var>b</var><span class="samp">,</span></samp>’, ‘<samp><span class="samp">rl</span></samp>’, ‘<samp><span class="samp">rlc</span></samp>’, ‘<samp><span class="samp">rr</span></samp>’, ‘<samp><span class="samp">rrc</span></samp>’,
‘<samp><span class="samp">sla</span></samp>’, ‘<samp><span class="samp">sli</span></samp>’, ‘<samp><span class="samp">sra</span></samp>’ and ‘<samp><span class="samp">srl</span></samp>’, and the register
‘<samp><var>r</var></samp>’ may be any of ‘<samp><span class="samp">a</span></samp>’, ‘<samp><span class="samp">b</span></samp>’, ‘<samp><span class="samp">c</span></samp>’, ‘<samp><span class="samp">d</span></samp>’,
‘<samp><span class="samp">e</span></samp>’, ‘<samp><span class="samp">h</span></samp>’ and ‘<samp><span class="samp">l</span></samp>’.
<br><dt><var>opc</var><code> (iy+</code><var>d</var><code>), </code><var>r</var><dd>As above, but with ‘<samp><span class="samp">iy</span></samp>’ instead of ‘<samp><span class="samp">ix</span></samp>’.
</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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