PC value in stack frame after exception entry remains 0x00000000.

[vishweshgm]

I am trying to understand the exception entry behaviour of cortex M3. It is given that stack frame contains PC info at address SP+0x18.

If I see the PC value after entry of SysTick_Handler(), it remains 0x0000 0000. Please refer screenshots to get idea on what I am trying to do.

I'm using ST's latest eclipse IDE.

Controller used is STM32F103C8.

ST-Link V2 debugger

[waclawek.jan · Accepted solution]

> It is given that stack frame contains PC info at address SP+0x18

Only if the handler itself did not put anything else on the stack. Observe the disasm of the handler.

JW

[vishweshgm]

Hello JW,

You are right. The disassembly shows the r7 and lr push. Can you help me understand the flow please. Where is the return point PC stored?

[waclawek.jan]

As you've now stopped before the push, offset 0x18 indeed contains the return value for PC, i.e. 0x08000642 (for some reason your debugger shows words MSB first - I don't use Eclipse).

JW

[vishweshgm]

Thank you. Memory view problem got solved after I changed Rendering option from hex to HexInteger in eclipse. Not sure why eclipse has not given option to change endianness in Hex view. Overall my issue got solved.