Re: Problem with representation clause

[Jeff <balderon@bigfoot.com>]

Fabrizio Castrotorres wrote:
>   type Measurement_Status_Value is range -2 .. 1;
>   for  Measurement_Status_Value'Size use 2;
>
>   type Slot_Number is range 0 .. 23;
>
>   type Integrity_Data is array (Slot_Number) of Measurement_Status_Value;
>   For Integrity_Data'Size use 24*2;   -- REPRESENTATION 1
>   pragma Pack(Integrity_Data);
>
>   type Global_Integrity_Array is array( Slot_Number ) of Integrity_Data;
>   For Global_Integrity_Array'Size use 24*48;  -- REPRESENTATION 2
>   pragma Pack(Global_Integrity_Array);
>
> [snip]
>
> size for "Global_Integrity_Array" too small, minimun allowed is 1536
> 
> The size I specified is             24*(24*2) = 1152 bits
> The size the compiler requires is   24*(32*2) = 1536 bits
> 

  You are running into an 8-bit alignment problem with your first
  array declaration. The compiler is assigning each element of the
  array as an 8-bit quanity. Right off hand, I cannot think of a 
  quick fix. If this is a hardware interface, I would redefine the
  declarations to access the status 8 bits at a time.

Jeff    
-- 
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\ Jeff Rooze - http://www.treknet.net/~jrooze - balderon@bigfoot.com /
/  If builders built buildings the way some programmers write        \
\  programs, then the first woodpecker that came along would destroy /
/  civilization.                                     GERALD WEINBERG \
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