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How to modify the program coutner in C program

Sh.Sasaki
Guru 13625 points
Other Parts Discussed in Thread: MSP430F5342

Hi All,

Do you know how to modify the PC(program coutner) in C program ?

MSP430F543x has errata CPU28 & CPU34.

I believe that we can program the C language to avoid this errata If I know the PC how to modify.

Best regards,

Mino.M

  • 0
    Guru 46710 points
    Would be great if you post link to document you are referring to.
  • 0
    Guru 58965 points
    Most c-compilers will automatically change PC by itself without your help. Some of them will work arround know CPU bugs. Some of them will even work arround non-existing CPU bugs.
  • 0 in reply to Ilmars
    Guru 13625 points

    Hi Ilmars,

    Thank you for your reply.

    I'm referring to the following documents.

    MSP430F5342 Device Erratasheet(5 & 7page)
    www.ti.com.cn/.../slaz278m.pdf

    Best regards,

    Mino.M

  • 0 in reply to old_cow_yellow
    Guru 13625 points

    Hi old_cow_yellow,

    Thank you for your answer.

    old_cow_yellow said:
    Most c-compilers will automatically change PC by itself without your help. Some of them will work arround know CPU bugs. Some of them will even work arround non-existing CPU bugs.

    I can not judge whether the compiler to avoid CPU bugs of CPU28 & CPU34.

    Best regards,

    Mino.M

  • 0 in reply to Sh.Sasaki
    Guru 58965 points
    You can inspect the object code they generate. You may find that there are planty of NOP here and there including the ones that can work around CPU28 & CPU34.
  • 0 in reply to old_cow_yellow
    Guru 13625 points

    Thank you for quick reply.

    old_cow_yellow said:
    You can inspect the object code they generate. You may find that there are planty of NOP here and there including the ones that can work around CPU28 & CPU34.

    I understand that it is not possible to care at the time of programming.

    In other words,  this errata(CPU28&34) can not be avoided unless I check the ASM output by the compiler.

    Best regards,

    Mino.M

  • 0
    Guru 227245 points
    Errata list situations where the system does not behave as expected or described. Sometimes it even lists things that ARE described in the users guide, but are not expected/surprising.
    However, those anomalies do not need to be sane at all.
    I don't know why someone should do a rotate PC operation. what good would it do to multiply the program counter by two or divide it by two? I can't figure out any real-world situation where CPU34 would hit.
    IMHO, the only indexed operation generated by a compiler where the PC is the target (CPU28) would be the __even_in_range() intrinsic, which adds the interrupt vector (xxIV) register to the PC for a jump table. In case the compiler doesn't take care of this itself (and usually, such errata are known and supported by the compiler), you can add a NOP right before the switch statement.

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