AVR_002dModifiers.html 6.0 KB

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  57. <a name="AVR_002dModifiers"></a>
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  59. <p>
  60. Previous: <a href="AVR_002dRegs.html#AVR_002dRegs" accesskey="p" rel="prev">AVR-Regs</a>, Up: <a href="AVR-Syntax.html#AVR-Syntax" accesskey="u" rel="up">AVR Syntax</a> &nbsp; [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p>
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  62. <hr>
  63. <a name="Relocatable-Expression-Modifiers"></a>
  64. <h4 class="subsubsection">9.5.2.3 Relocatable Expression Modifiers</h4>
  65. <a name="index-AVR-modifiers"></a>
  66. <a name="index-syntax_002c-AVR"></a>
  67. <p>The assembler supports several modifiers when using relocatable addresses
  68. in AVR instruction operands. The general syntax is the following:
  69. </p>
  70. <div class="smallexample">
  71. <pre class="smallexample">modifier(relocatable-expression)
  72. </pre></div>
  73. <dl compact="compact">
  74. <dd><a name="index-symbol-modifiers"></a>
  75. </dd>
  76. <dt><code>lo8</code></dt>
  77. <dd>
  78. <p>This modifier allows you to use bits 0 through 7 of
  79. an address expression as 8 bit relocatable expression.
  80. </p>
  81. </dd>
  82. <dt><code>hi8</code></dt>
  83. <dd>
  84. <p>This modifier allows you to use bits 7 through 15 of an address expression
  85. as 8 bit relocatable expression. This is useful with, for example, the
  86. AVR &lsquo;<samp>ldi</samp>&rsquo; instruction and &lsquo;<samp>lo8</samp>&rsquo; modifier.
  87. </p>
  88. <p>For example
  89. </p>
  90. <div class="smallexample">
  91. <pre class="smallexample">ldi r26, lo8(sym+10)
  92. ldi r27, hi8(sym+10)
  93. </pre></div>
  94. </dd>
  95. <dt><code>hh8</code></dt>
  96. <dd>
  97. <p>This modifier allows you to use bits 16 through 23 of
  98. an address expression as 8 bit relocatable expression.
  99. Also, can be useful for loading 32 bit constants.
  100. </p>
  101. </dd>
  102. <dt><code>hlo8</code></dt>
  103. <dd>
  104. <p>Synonym of &lsquo;<samp>hh8</samp>&rsquo;.
  105. </p>
  106. </dd>
  107. <dt><code>hhi8</code></dt>
  108. <dd>
  109. <p>This modifier allows you to use bits 24 through 31 of
  110. an expression as 8 bit expression. This is useful with, for example, the
  111. AVR &lsquo;<samp>ldi</samp>&rsquo; instruction and &lsquo;<samp>lo8</samp>&rsquo;, &lsquo;<samp>hi8</samp>&rsquo;, &lsquo;<samp>hlo8</samp>&rsquo;,
  112. &lsquo;<samp>hhi8</samp>&rsquo;, modifier.
  113. </p>
  114. <p>For example
  115. </p>
  116. <div class="smallexample">
  117. <pre class="smallexample">ldi r26, lo8(285774925)
  118. ldi r27, hi8(285774925)
  119. ldi r28, hlo8(285774925)
  120. ldi r29, hhi8(285774925)
  121. ; r29,r28,r27,r26 = 285774925
  122. </pre></div>
  123. </dd>
  124. <dt><code>pm_lo8</code></dt>
  125. <dd>
  126. <p>This modifier allows you to use bits 0 through 7 of
  127. an address expression as 8 bit relocatable expression.
  128. This modifier useful for addressing data or code from
  129. Flash/Program memory. The using of &lsquo;<samp>pm_lo8</samp>&rsquo; similar
  130. to &lsquo;<samp>lo8</samp>&rsquo;.
  131. </p>
  132. </dd>
  133. <dt><code>pm_hi8</code></dt>
  134. <dd>
  135. <p>This modifier allows you to use bits 8 through 15 of
  136. an address expression as 8 bit relocatable expression.
  137. This modifier useful for addressing data or code from
  138. Flash/Program memory.
  139. </p>
  140. </dd>
  141. <dt><code>pm_hh8</code></dt>
  142. <dd>
  143. <p>This modifier allows you to use bits 15 through 23 of
  144. an address expression as 8 bit relocatable expression.
  145. This modifier useful for addressing data or code from
  146. Flash/Program memory.
  147. </p>
  148. </dd>
  149. </dl>
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