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Strange thing: R10 register's value is modified after this instruction "inc.b R14"

Jiangfei Gu
Prodigy 20 points
Other Parts Discussed in Thread: MSP430F417

Hi expert,

A strange problem happened to me: I use IAR develop C program for MSP430F417 MCU, a problem happened, and I checked the Disassembly code. Then, I found that the R10 register's value is modified after this instruction "inc.b R14". Shown as bellow:

(R14 stored the first parameter of a function: void dsStoreData( uint8_t* destination, uint8_t* data, uint8_t size ))

figure1: the disassembly window:

 

figure 2: before run the "inc.b R14" instruction, (stopped on this instrunction)

 

 

figure 3: after pressing "F11"(step in), the PC was not changed, but R14 changed, and R10 was also changed

 

  • 0
    Guru 227245 points

    The assembly code around your breakpoint would be interesting.

    By itself the mentioned assembly instruction won't alter R10, but only R14 (or else almost no program would ever work).

  • 0
    Genius 4925 points

    I'm not sure about the IAR debuggers behaviour, but in case of CCS the step into will step a complete C code line, and if it's a function call then it will step into that function.

    This might turn out to be quite a lot assembler statements which are stepped over to get to the next C code line - and maybe you are not seeing what you would expect.

    On CCS there is an additional button for assembly single stepping (in the disassembly view) for fine control.

    Only a guess into the blue. 

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