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Array Indexing in VHDL

I have an array:

type offsets_type is array (4 downto 0) of std_logic_vector (4 downto 0); 
signal av     : offsets_type;

I want to do this essentially: av[addr] += 1;
But this line:

 av(to_integer(unsigned(addr))) <= unsigned(av(to_integer(unsigned(addr))) + 1;

gives this error:
to_integer can not have such operands in this context.

I also tried using conv_integer, but this gives Wrong type of indexas an error.

Any solutions? Thank.

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1 answer

There are several problems in the code:

  • You pass the result of your calculation to unsigned, and the left side -std_logic_vector
  • There may be something wrong with the data type addr, but you have not shared this with us.
  • There is no closing parenthese in the assignment.

This will be easier if you use "unsigned" in your type definitions. This way you express that the bit pattern is what you want to use in integer arithmetic.

type offsets_type is array (4 downto 0) of unsigned (4 downto 0);
signal av     : offsets_type;
signal addr :unsigned(2 downto 0);

This will save several type conversions:

av(to_integer(addr)) <= av(to_integer(addr)) + "1";

Edit: you used ieee.numeric_std.all, right?

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