Scalar types

• enumeration_type_definition
• integer_type_definition
• floating_type_definition
• physical_type_definition

Different types are declared.

• Types Bit and switch_level are declared as enumeration types through characters and can only have the values ' 0' or ' 1' and 'X '. One has to distinguish between these values '0 ' and '1' and the integer values 0 and 1 . Both characters are overloaded.
• Types states and colours are declared as enumeration types by self-explanatory element names.

TYPE Bit IS ( '0', '1' ) ;
 
TYPE switch_level IS ( '0', '1', 'X' ) ;
 
TYPE states IS (out, sleeping, working);
 
TYPE colors IS ( red, green, blue );

• Integer types are generated by stating integral numbers in the range declaration (RANGE).
• The range can be declared rising (TO) or falling (DOWNTO).
• Real types are created through realistic range declarations.
• Subtypes can be declared by stating the base type and the selected range.

TYPE byte_length_integer IS
             RANGE 0 TO 255 ;
 
TYPE word_index IS RANGE 31 DOWNTO 0 ;
 
TYPE my_real IS RANGE 0.0 TO 9.99 ;
 
SUBTYPE high_bit_low IS byte_length_integer
      RANGE 0 TO 127 ;

With physical types a real-type is defined first. Afterwards the basic unit and its derivative units are declared.

As examples the definitions of the units of length (distance) and the units of time (time) are shown here.

The physical unit time is a predefined type.

TYPE distance IS RANGE 0 TO 1E16
   UNITS
      -- Basiseinheit :
         A -- Angström
      -- Metrische Einheiten :
         nm  =  10 A ;    -- Nanometer
         um  =  1000 nm ;  -- Mikrometer
         mm  =  1000 um ;  -- Millimeter
         cm  =  10 mm ;  -- Centimeter
         m  =  1000 mm ;  -- Meter
         km  =  1000 m ;   -- Kilometer
   END UNITS ;
 
TYPE time IS RANGE -1E18 TO 1E18
   UNITS
      fs ;  --Femtosekunde
      ps   = 1000 fs ;  -- Picosecond
      ns   = 1000 ps ;  -- Nanosecond
      us   = 1000 ns ;  -- Microsecond
      ms   = 1000 us ;  -- Millisecond
      sec  = 1000 ms ;  -- Second
      min  = 60 sec ;   -- Minute
   END UNITS