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| <h4 class="subsection">9.22.3 Symbolic Operand Modifiers</h4> |
| |
| <p><a name="index-M68HC11-modifiers-1218"></a><a name="index-syntax_002c-M68HC11-1219"></a> |
| The assembler supports several modifiers when using symbol addresses |
| in 68HC11 and 68HC12 instruction operands. The general syntax is |
| the following: |
| |
| <pre class="smallexample"> %modifier(symbol) |
| </pre> |
| |
| <a name="index-symbol-modifiers-1220"></a> |
| <dl><dt><code>%addr</code><dd>This modifier indicates to the assembler and linker to use |
| the 16-bit physical address corresponding to the symbol. This is intended |
| to be used on memory window systems to map a symbol in the memory bank window. |
| If the symbol is in a memory expansion part, the physical address |
| corresponds to the symbol address within the memory bank window. |
| If the symbol is not in a memory expansion part, this is the symbol address |
| (using or not using the %addr modifier has no effect in that case). |
| |
| <br><dt><code>%page</code><dd>This modifier indicates to use the memory page number corresponding |
| to the symbol. If the symbol is in a memory expansion part, its page |
| number is computed by the linker as a number used to map the page containing |
| the symbol in the memory bank window. If the symbol is not in a memory |
| expansion part, the page number is 0. |
| |
| <br><dt><code>%hi</code><dd>This modifier indicates to use the 8-bit high part of the physical |
| address of the symbol. |
| |
| <br><dt><code>%lo</code><dd>This modifier indicates to use the 8-bit low part of the physical |
| address of the symbol. |
| |
| </dl> |
| |
| <p>For example a 68HC12 call to a function ‘<samp><span class="samp">foo_example</span></samp>’ stored in memory |
| expansion part could be written as follows: |
| |
| <pre class="smallexample"> call %addr(foo_example),%page(foo_example) |
| </pre> |
| <p>and this is equivalent to |
| |
| <pre class="smallexample"> call foo_example |
| </pre> |
| <p>And for 68HC11 it could be written as follows: |
| |
| <pre class="smallexample"> ldab #%page(foo_example) |
| stab _page_switch |
| jsr %addr(foo_example) |
| </pre> |
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