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Initial PC address for KL25 does not match?

Question asked by Antonio Quevedo on Jul 19, 2013
Latest reply on Jul 20, 2013 by Antonio Quevedo

I am using the FRDM-KL25 board as a tool for teaching basic software in an engineering course. As I am creating experiments, and executing them myself, I found something strange.

 

At Reset, Kinetis L processors first fetch the initial SP address at 0x00000000 position. Then, it fetchse initial PC address at 0x00000004 position. When I created a project in CodeWarrior 10.4, I used Debugger Shell to read memory contents, and found the following values (corrected for endianess):

 

SP: 0x20003000; PC: 0x0000085D

 

Strange, PC address does not seem to be aligned in a 4-byte boundary. And when I look in the assembly code, at the Disassembly window, I see startup code (label __thumb_startup) at 0x0000085C address.

 

Can someone explain why CodeWarrior generates a code that commands CPU to fetch one memory position after the one it should? And why the program runs OK even with this supposed error? I expect to comment that on my course.

 

Thanks in advance,

 

Antonio Quevedo

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