https://devzone.nordicsemi.com/f/nordic-q-a/28795/how-i-solve-the-problem-in-keil5-error-65-access-violation-at-0xfffffff4-no-write-permissionwhen I used simulator in keil5 for NRF51 software debug, there is a problem : *** error 65: access violation at 0xFFFFFFF4 : no &#39;write&#39; permission. When I used the keil5 command &quot;Map 0xFFFF0000,0xFFFFFFFF READ WRITE&quot;, the error disappeared. But, theen-USTelligent Community 13Wed, 05 May 2021 09:34:42 GMThttps://devzone.nordicsemi.com/thread/308312?ContentTypeID=1Wed, 05 May 2021 09:34:42 GMT137ad170-7792-4731-bb38-c0d22fbe4515:a83b57ae-acdc-48ac-ad60-80673f592f8fwid107<p>how did you solve this problem? Would be great if you could reply. I am stuck and could not proceed. Thanks in advance</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/114079?ContentTypeID=1Fri, 29 Dec 2017 12:01:36 GMT137ad170-7792-4731-bb38-c0d22fbe4515:5ca740ba-f3dd-44cc-9fb2-86a25fc2512cHung Bui<p>I don&#39;t think the simulator works with our code. You may want to get hold of a nRF5 DK for development. Please be aware that latest softdevice for nRF51 is S130 v2.0. And nRF52 is suggested for new product development.</p><div style="clear:both;"></div>