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<h2>
<a name="1208326"> </a><font color="#003366" face="Verdana, Arial, Helvetica, sans-serif">9.2 An example program and target configuration</font>
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<p>
<a name="1208327"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The <font size=2 face=Courier><strong>examples/romdebug</strong></font> directory contains an example which illustrates key issues with debugging ROM systems, and uses some common set-top box software features. The program prints out a set of messages while flashing an LED, then uses the onchip watchdog timer to reset itself.</font>
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<a name="1204471"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">If the target is reset (for example, by a watchdog timer) while <strong>st20run</strong> is connected, the target will stall. The target can only be recovered from the stall state by using the <font size=2 face=Courier><strong>restart</strong></font> command. The example calls the function <font size=2 face=Courier><strong>debugcommand</strong></font> to execute a command language procedure which performs a restart after a watchdog reset has occurred.</font>
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<a name="1204472"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The examples below apply to an STi5500 device on an EVAL-5500 board. They may be run on an ST20TP3 device on an STB3-EVAL board by replacing instances of <font size=2 face=Courier><strong>STi5500MB159</strong></font> with <font size=2 face=Courier><strong>ST20TP3MB193B</strong></font> and adding a target definition to the <font size=2 face=Courier><strong>example.cfg</strong></font> file (using the existing definition as a basis, <font size=2 face=Courier><strong>mk_STi5500_MB159_gen</strong></font> could be replaced with <font size=2 face=Courier><strong>mk_ST20TP3_MB193B_gen</strong></font> and <font size=2 face=Courier><strong>keen</strong></font> with the name of the target board).</font>
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<a name="1204473"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The example can be built and debugged as a linked unit or as a ROM image.</font>
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<a name="1204474"> </a><font size=2 face="Verdana, Arial, Helvetica, sans-serif">The definition of targets using the <font size=2 face=Courier><strong>mk_<chip_type>_<board_type>_gen</strong></font> command language procedures defines targets using the default board specification procedures which can be found in the <font size=2 face=Courier><strong>boards</strong></font> directory. These default board specification procedures are used by both <strong>st20cc</strong> when linking and <strong>st20run</strong> when loading and debugging. Examining these default procedures, we find several commands key to target definition.</font>
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<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204475"> </a>The <font size=2 face=Courier><strong>chip</strong></font> command specifies the variant of the ST20, and defines:</font></p>
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<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204476"> </a>the processor core type,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204477"> </a>the system memory, declared to be <font size=2 face=Courier><strong>RESERVED</strong></font>,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204478"> </a>the internal memory,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204479"> </a>cache and interrupt management,</font></p>
<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204483"> </a>a watchdog keep-alive trap handler (see the <em>ST20 Embedded Toolset User Manual</em>, chapter <em>st20run tool</em>).</font></p>
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<p> <font size=2 face="Verdana, Arial, Helvetica, sans-serif"><li ><a name="1204486"> </a>The <font size=2 face=Courier><strong>memory</strong></font> command specifies a memory segment; for full details, see <a href="commands.htm#1212189"><font color="#0000ff" face="Verdana, Arial, Helvetica, sans-serif"><i>Chapter⌨️ 快捷键说明
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