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<title>CMSIS-Core (Cortex-M): Using Interrupt Vector Remap</title>
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<div class="title">Using Interrupt Vector Remap </div> </div>
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<div class="textblock"><p>Most Cortex-M processors provide VTOR register for remapping interrupt vectors. The following example shows a typical use case where the interrupt vectors are copied to RAM and the SysTick_Handler is replaced.</p>
<div class="fragment"><div class="line"><span class="preprocessor">#include &quot;ARMCM3.h&quot;</span> <span class="comment">// Device header</span></div>
<div class="line"> </div>
<div class="line"><span class="comment">/* externals from startup_ARMCM3.s */</span></div>
<div class="line"><span class="keyword">extern</span> uint32_t __Vectors[]; <span class="comment">/* vector table ROM */</span></div>
<div class="line"> </div>
<div class="line"><span class="preprocessor">#define VECTORTABLE_SIZE (256) </span><span class="comment">/* size Cortex-M3 vector table */</span><span class="preprocessor"></span></div>
<div class="line"><span class="preprocessor"></span><span class="preprocessor">#define VECTORTABLE_ALIGNMENT (0x100ul) </span><span class="comment">/* 16 Cortex + 32 ARMCM3 = 48 words */</span><span class="preprocessor"></span></div>
<div class="line"><span class="preprocessor"></span> <span class="comment">/* next power of 2 = 256 */</span></div>
<div class="line"> </div>
<div class="line"><span class="comment">/* new vector table in RAM */</span></div>
<div class="line">uint32_t vectorTable_RAM[VECTORTABLE_SIZE] __attribute__(( aligned (VECTORTABLE_ALIGNMENT) ));</div>
<div class="line"> </div>
<div class="line"><span class="comment">/*----------------------------------------------------------------------------</span></div>
<div class="line"><span class="comment"> SysTick_Handler</span></div>
<div class="line"><span class="comment"> *----------------------------------------------------------------------------*/</span></div>
<div class="line"><span class="keyword">volatile</span> uint32_t msTicks = 0; <span class="comment">/* counts 1ms timeTicks */</span></div>
<div class="line"><span class="keywordtype">void</span> SysTick_Handler(<span class="keywordtype">void</span>) {</div>
<div class="line"> msTicks++; <span class="comment">/* increment counter */</span></div>
<div class="line">}</div>
<div class="line"> </div>
<div class="line"><span class="comment">/*----------------------------------------------------------------------------</span></div>
<div class="line"><span class="comment"> SysTick_Handler (RAM)</span></div>
<div class="line"><span class="comment"> *----------------------------------------------------------------------------*/</span></div>
<div class="line"><span class="keyword">volatile</span> uint32_t msTicks_RAM = 0; <span class="comment">/* counts 1ms timeTicks */</span></div>
<div class="line"><span class="keywordtype">void</span> SysTick_Handler_RAM(<span class="keywordtype">void</span>) {</div>
<div class="line"> msTicks_RAM++; <span class="comment">/* increment counter */</span></div>
<div class="line">}</div>
<div class="line"> </div>
<div class="line"><span class="comment">/*----------------------------------------------------------------------------</span></div>
<div class="line"><span class="comment"> MAIN function</span></div>
<div class="line"><span class="comment"> *----------------------------------------------------------------------------*/</span></div>
<div class="line"><span class="keywordtype">int</span> main (<span class="keywordtype">void</span>) {</div>
<div class="line"> uint32_t i;</div>
<div class="line"> </div>
<div class="line"> <span class="keywordflow">for</span> (i = 0; i &lt; VECTORTABLE_SIZE; i++) {</div>
<div class="line"> vectorTable_RAM[i] = __Vectors[i]; <span class="comment">/* copy vector table to RAM */</span></div>
<div class="line"> }</div>
<div class="line"> <span class="comment">/* replace SysTick Handler */</span></div>
<div class="line"> vectorTable_RAM[<a class="code" href="group__NVIC__gr.html#gga7e1129cd8a196f4284d41db3e82ad5c8a6dbff8f8543325f3474cbae2446776e7">SysTick_IRQn</a> + 16] = (uint32_t)SysTick_Handler_RAM;</div>
<div class="line"> </div>
<div class="line"> <span class="comment">/* relocate vector table */</span> </div>
<div class="line"> <a class="code" href="group__Core__Register__gr.html#gaeb8e5f7564a8ea23678fe3c987b04013">__disable_irq</a>();</div>
<div class="line"> SCB-&gt;VTOR = (uint32_t)&amp;vectorTable_RAM;</div>
<div class="line"> <a class="code" href="group__intrinsic__CPU__gr.html#gacb2a8ca6eae1ba4b31161578b720c199">__DSB</a>();</div>
<div class="line"> <a class="code" href="group__Core__Register__gr.html#ga0f98dfbd252b89d12564472dbeba9c27">__enable_irq</a>();</div>
<div class="line"> </div>
<div class="line"> <a class="code" href="group__system__init__gr.html#gae0c36a9591fe6e9c45ecb21a794f0f0f">SystemCoreClockUpdate</a>(); <span class="comment">/* Get Core Clock Frequency */</span></div>
<div class="line"> <a class="code" href="group__SysTick__gr.html#gabe47de40e9b0ad465b752297a9d9f427">SysTick_Config</a>(<a class="code" href="group__system__init__gr.html#gaa3cd3e43291e81e795d642b79b6088e6">SystemCoreClock</a> / 1000ul); <span class="comment">/* Setup SysTick Timer for 1 msec */</span></div>
<div class="line"> </div>
<div class="line"> <span class="keywordflow">while</span>(1);</div>
<div class="line">}</div>
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