• Resolved

_IER undefined?


I have a .cpp file that uses IER. When trying to compile it, it gives:

ERROR!   at EOF: [E0300]
1 Assembly Error, No Assembly Warnings
         The following symbols are undefined:

Errors in Source - Assembler Aborted

According to the "TMS320C28x Assembly Language Tools v6.0", section 3.9.5, CPU control registers are predefined, especially IER.

What's going on?

Many thanks for your help,


  • In C/C++ code, you have to explicitly declare the control registers like this ...

    extern cregister volatile unsigned int IFR;
    extern cregister volatile unsigned int IER;
    Thanks and regards,

    TI C/C++ Compiler Forum Moderator
    Please click This Resolved My Issue on the best reply to your question
    The CCS Youtube Channel
     has short how-to videos
    Compiler Wiki answers most common questions
    Track an issue with SDOWP. Enter your bug id in the Search box.

  • In reply to George Mock:

    Dear George,

    These are already defined in "DSP281x_Device.h" as far as I can see, and I include "DSP281x_Device.h" in my source file.

    I however found out that there is a problem only when I use "IER" directly as an argument of a function call. If I don't use it as an argument, it complies properly?!?!?!


    Thank you anyway,


  • In reply to Investigator:

    I cannot reproduce this problem.  Please double-check that the cregister declaration really is present when you compile your file by adding the --preproc_only command-line argument and inspecting the resulting .pp file.  If it is present, and you still get that error message, please post a compilable test case which reproduces the problem.

  • In reply to Archaeologist:

    Dear Archeologist,

    To reproduce the problem, create a new project in CCS4 with a target of TMS320F2812. I use CGT 6.0.1.

    Then add a "main.cpp" file and populate it thus:

    #include "DSP281x_Device.h"

    void fn(volatile Uint16& reg)
        reg = 0;

    int main()

    Then try to build, and you should get the error.

    Best regards,


  • In reply to Investigator:

    The issue here is that you are attempting to create a C++ reference to IER, which is not supported by the TI compiler.  Taking the address of a cregister is also not supported.  The parser ought to have rejected this with an error, and the fact that it did not is a bug (now SDSCM00043533).

    Here's a cutdown test case:

    extern cregister volatile unsigned int IER;
    void fn(volatile unsigned & reg);
    int main() { fn(IER); }

    You'll need to write this code like this:

    void clear_IER(void) { IER = 0; }