Re: Storage space question

[stt@houdini.camb.inmet.com (Tucker Taft)]

Marin David Condic (condicma@bogon.pwfl.com) wrote:

: ...
: If you can't find an answer in the compiler-specific documentation, you
: can always get there through the
: less-desirable-but-no-worse-than-C-does-it method of declaring a bunch
: of named numbers:

: Some_Name : constant := 2#0101# ;

: It does, as you observe, have name-space problems, but it will get you
: there. 

Actually, rather than using named numbers, I would recommend
using named constants of a derived integer type devoted to this
particular machine register.  This way, you would at least 
get some type checking when you have more than one such machine
register.

E.g.:
   type DMA_Register_Command is range 0..2#1111#;
   
   Start_DMA_Transfer : constant DMA_Register_Command := 2#0101#;
   ... 

Personally, I would only use enumerations for things which are
clearly enumerable.  Machine registers often use combinations of
bits, which are easily done with "+" for integers (or with "or"
in Ada 95 on modular types), but not easily done with enumeration types.

: MDC
: -- 
: Marin David Condic
: Real Time & Embedded Systems, Propulsion Systems Analysis
: United Technologies, Pratt & Whitney, Large Military Engines
: M/S 731-95, P.O.B. 109600, West Palm Beach, FL, 33410-9600
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-Tucker Taft   stt@inmet.com   http://www.inmet.com/~stt/
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