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Byte wide access to OCOTP->LOCK address seems to hang the CPU...

Question asked by Ed Sutter on Apr 21, 2020
Latest reply on Apr 29, 2020 by Ed Sutter


I'm working on an MIMXRT1060-EVK.  I'm doing some work with the OCOTP and I accidentally read from address 0x401f0400 (LOCK register) with a byte-wide access.  Clearly this is illegal.  My firmware catches all exceptions, but what I noticed was that my running program just hung (i.e. no longer responsive).  So, I attached my Segger JLINK and ran the [illegal] code again hoping that I could halt the core to see where the code was after that access (thinking maybe my exception handling was the problem).  I got a response from JLINK:  


WARNING: CPU could not be halted

Is this expected?  What is the state of the CPU if JLINK can't halt it?  Shouldn't that illegal access have caused the processor to at-least take a hard-fault exception?

Any thoughts?