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Unions version 2

 
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dxrose86



Joined: 28 Feb 2009
Posts: 5
Location: Taunton Ma

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Unions version 2
PostPosted: Thu Jan 21, 2010 1:47 pm     Reply with quote
Processor Pic18f26K20
Compiler version 4.099

Problem: I am trying to use bit fields inside a union.
My program looks like

Code:
union {
int1 bright1;
int1 bright2;
int1 bright3;
int1 bright4;
int1 bright5;
int1 bright6;
int1 functionb1;
int1 notused1b7;
int8 bytem;
}msgd;

void main ()
 {
  msgd.bytem = 0xaa;
 

  if (msgd.functionb1 == 1)
    msgd.functionb1 = 0;

}

/* end of program */

The bit field accessess bit 6 of the byte field. but generates the following code:
Code:

116:                     if (msgd.functionb1 == 1)
 
02F4    A176             BTFSS 0x76, 0, BANKED
 
02F6    D001             BRA 0x2fa
117:
                                msgd.functionb1 = 0;
 
02F8    9176     BCF 0x76, 0, BANKED

The generated code will access bit 0 only no matter what bit field I try.
any suggestions would be appreciated.
Thanks
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Micro-guy
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Thu Jan 21, 2010 2:26 pm     Reply with quote
See Ttelmah's example of bitfields in a union here:
http://www.ccsinfo.com/forum/viewtopic.php?t=28773&start=3

Also, please don't start a new thread every time you have a new
question on Unions. Add the question onto your existing thread.
The thread will "bump" to the top of the list. We will see it, and
it will be noticed.
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Thu Jan 21, 2010 3:30 pm     Reply with quote
Quote:
The generated code will access bit 0 only no matter what bit field I try.
That's exactly, what you should expect from a union, you possibly mean a struct instead?
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