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Struct number of bits out of range error

 
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Tom-H-PIC



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Struct number of bits out of range error
PostPosted: Mon Feb 28, 2011 1:18 pm     Reply with quote
Hello
Can someone tell me why this?
If I define the struct with element 2 as 4 bits it compiles without an issue.

Code:

struct wwvbtime {    //top 32 bits received
   int   nu1;        //top 8 bits of 32 not used
   int   nu2   :4;   //next 7 bits of 32 not used
   int   mt    :3;   //tens of minutes
   int   nu3   :1;   //one bit not used
   int   m     :4;   //minutes
   int   nu4   :2;   //two bits not used
   int   ht    :2;   //tens of hours
   int   nu5   :1;   //one bit not used
   int   h     :4;   //hours
} rxhigh;


But if I replace the 4 bits with 7 bits I get a compiler error.
"Number of bits is out of range"
With 7 bits in element 2 would make the total bits in the struct = 32.

Code:

struct wwvbtime {    //top 32 bits received
   int   nu1;        //top 8 bits of 32 not used
   int   nu2   :7;   //next 7 bits of 32 not used
   int   mt    :3;   //tens of minutes
   int   nu3   :1;   //one bit not used
   int   m     :4;   //minutes
   int   nu4   :2;   //two bits not used
   int   ht    :2;   //tens of hours
   int   nu5   :1;   //one bit not used
   int   h     :4;   //hours
} rxhigh;


Compiler 4.119 PIC18F4550
PCM programmer



Joined: 06 Sep 2003
Posts: 21708

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PostPosted: Mon Feb 28, 2011 2:38 pm     Reply with quote
You may have to email CCS for a clarification on this.

Previous threads on this topic:
Quote:
Number of bits is out of range

http://www.ccsinfo.com/forum/viewtopic.php?p=91585
http://www.ccsinfo.com/forum/viewtopic.php?p=71262
FvM



Joined: 27 Aug 2008
Posts: 2337
Location: Germany

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PostPosted: Mon Feb 28, 2011 4:32 pm     Reply with quote
Yes, the compiler is expecting the bit fields to be aligned to byte boundaries.
Tom-H-PIC



Joined: 08 Sep 2003
Posts: 105
Location: New Castle, DE

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What about the 3 LSBs?
PostPosted: Mon Feb 28, 2011 5:14 pm     Reply with quote
Ok is that from top (MSB) to bottom (LSB)?
I assume that is true MSB top to LSB bottom what does it do with the 3 LSB that are not declared?
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