I am looking at some VHDL code and the following lines are present:
type obj_code_t is array(integer range <>) of std_logic_vector(7 downto 0);
and
OBJ_CODE : obj_code_t;
What does the <> signify?
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1\$\begingroup\$ IEEE Std 1076-2008 5.3.2 Array types, 5.3.2.1 "... The values of the left and right bounds of each index range are not defined, but shall belong to the corresponding index subtype; similarly, the direction of each index range is not defined. The symbol <> (called a box) in an index subtype definition stands for an undefined range (different objects of the type need not have the same bounds and direction)." \$\endgroup\$– user8352Jun 7, 2018 at 0:25
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1 Answer
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The "array(integer range <>)" syntax is used to declare an array with an unconstrained length.
See this page for detailed info on VHDL ranges. Some snippets from the page are shown below.
An example of an unconstrained array definition:
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\$\begingroup\$ Changed in -2008 to unbounded array definition where the element subtype can be unconstrained as well as the array index inheriting subtype from the index type. See IEEE Std 1076-2008 5.3.2 Array types, 5.3.2.1. \$\endgroup\$– user8352Jun 8, 2018 at 2:45