title: ARMv6-M memory protection unit
body: <p>While reading the <a href="https://c4everyone.com/pub/ARM/DDI0419C.pdf" rel="nofollow noreferrer">documentation of ARMv6-M</a>, I met for the first time the memory protection unit (which is not that complicated). According to the documentation, there is a register named the MPU_RASR (which stands for &quot;MPU Region Attribute and Size Register&quot;) and clearly there is more than one of the register (one for each memory region if I understood correctly). My question is how can I know how many replicas of this registers exists?
  (I reached this part of the documentation from the for loop in the ValidateAddress function description - <code>bits(16) size_enable = MPU_RASR[r]&lt;15:0&gt;;</code> (&quot;r&quot; is the iterator)</p>