title: Switching to privileged mode in cortex-m3
body: <p>I'm trying to access the SysTick timer of Cortex-M3 so I've to switch to priviledged mode. I'm doing it as</p>
  
  <pre><code>/* Active previlige mode */
  asm ("mov r0, #0x0");
  asm ("msr control, r0");
  asm ("ISB");
  </code></pre>
  
  <p>But it's not working because I'm unable to write the SYST_CSR register. Any exception entry is required to perform this operation if YES, how?</p>