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TMS320F2800157: CCS bit left shift

Manas Gupta
Prodigy 20 points
Part Number: TMS320F2800157


Hi,

I was just facing a problem in CCS where in I had to left shift bits by more than 15 places and it just dropped them off completely.

I have attached an image showing the code and the variable values. I need to shift the bits because the ref manual says 

  • 0
    TI__Guru**** 472441 points

    Hello,

    I'm assuming the issue is with how the variable is displayed in the Expressions view.

    I will try this out locally with my F2800157 target when I have access to it next week on Tuesday. Please note that Monday is a local holiday.

    Thanks

    ki

  • 0 in reply to Ki
    Prodigy 20 points

    Hi,

    sorry for my late reply, sat and sun were local holiday for us.

    its not just how variables are displayed in expressions view, when I push the value to the register  its is the same as displayed in expressions view and peripheral doesn't work as intended

    Thanks 

    Manas

  • 0 in reply to Manas Gupta
    TI__Guru**** 472441 points

    Thank you for the additional details. I will take a closer look when I return to the office tomorrow.

  • +1 in reply to Ki
    TI__Guru**** 251270 points

    The problem is this expression ...

    (uint32_t)(1 << 31)

    ... does not work as you expect.  The type of the constant value 1 is int.  In the C2000 compiler, an int is 16-bits wide.  In C, if the shift amount is greater than or equal to the width of the left operand, the behavior is undefined.  The C2000 compiler issues a diagnostic similar to ...

    "file.c", line 5: warning: shift count is too large

    ... and changes the expression to 0.  Rewrite it ...

    (1L << 31)
     

    The L suffix to the constant 1 changes the type to long.  The type long is 32-bits wide.  That works as you expect.

    Thanks and regards,

    -George