Accessing bit fields using a union problem.

Hello - I changed my code from my last post:
http://cboard.cprogramming.com/showthread.php?t=109945
so that the struct of bit fields is unionized with a UINT32 word:

Code:

---

#include <stdio.h>


typedef union
{
    struct {

    /// Reserved - read as 0
    unsigned reserved : 30;

    /** This bit contains the interrupt status. Reading this register
    * clears this bit.
    */
    unsigned stats : 1;

    /** This field masks the interrupt.
    *        0 - Masked
    *        1 - Enabled
    */
    unsigned maskn : 1;

    } bits;

    unsigned long word;

} volatile RegStruct;

RegStruct *hwReg

---

When I print out hwReg.word I get the entire correct 32 bits - BUT when I print out one of the bits hwReg.bits.maskn, I get 0x00000000 - I think it still may be accessing the bits as bytes even though the struct is unionized with UINT32. what is going on?

I assume you're printing with %x? %x says "the thing I am handing you is an unsigned int". If the thing you are printing is not an unsigned int, well, then, that's too bad -- it's going to be printed as an unsigned int.

Why yes we are printing with a %x and all the bytes that are displayed are positive status bits, so they are unsigned. Can you please help still?

Show us the code that does the printing.

--
Mats

Code:

---

void putHex(UINT32 x)
{
    printf("0x%x ", x);
}

---

but could it have to do with something about union and struct in my code instead?

Have you by any chance intialized RegStruct.word as well as RegStruct.bits.maskn or any other bit variable? That is not advisable when using a union as they share the same memory of the larger of the two defined variables.

Right, can you please post all (or at least a decent part) of the code, as we need some context to answer this question, I think.

--
Mats