Record Types

A record is a set of named fields of various types, unlike an array, which is composed of identical anonymous entries. A record's field can be any previously defined type, including another record type.

The following example shows a record type declaration (BYTE_AND_IX), three signals of that type, and some assignments.

constant LEN:  INTEGER := 8;

subtype BYTE_VEC is BIT_VECTOR(LEN-1 downto 0);

type BYTE_AND_IX is 

  record

    BYTE: BYTE_VEC;

    IX:   INTEGER range 0 to LEN;

  end record; 

signal X, Y, Z: BYTE_AND_IX;

signal DATA: BYTE_VEC;

signal NUM:  INTEGER;

. . .

X.BYTE <= "11110000";

X.IX   <= 2;

DATA <= Y.BYTE;

NUM  <= Y.IX;

Z <= X;

As shown in the above example, you can read values from or assign values to records in two ways.

• By individual field name
  
  

  X.BYTE <= DATA;
  
  X.IX   <= LEN;

  
  
  
• From another record object of the same type
  
  Z <= X;
  
  

The individual fields of a record type object are accessed by the object name, a period, and a field name; X.BYTE or X.IX. To access an element of the BYTE field's array, use the array notation X.BYTE(2).