====== Bit string literals ======
===== Definition =====
==== bit_string_literal ====
  base_specifier " [ bit_value ] "

==== base_specifier ====
  * B
  * O
  * X

==== bit_value ====
  extended_digit { [ underline ] extended_digit }

==== extended_digit ====
  * digit
  * letter

===== Comments =====
B means binary, O means octal and X means hexadecimal.

===== Examples =====
<code vhdl>
Bit_8: bit_vector(7 downto 0) := B"1111_1111" -- equivalent to "11111111"

Bit_8 : bit_vector(7 downto 0) := X"FF"   -- equivalent to B"1111_1111"

Bit_9 : bit_vector(8 downto 0) := O"777"    -- equivalent to B"111_111_111"

Bit_12: bit_vector(11 downto 0) := X"777"   -- equivalent to B"0111_0111_0111"
</code>