--
-- Package mpis
--
library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
package mpis is
function seven_segment_decoder( hex : unsigned(3 downto 0)) return std_logic_vector;
function are_equal( vector: unsigned; number: natural) return boolean;
function format_diff( expected: integer; actual: integer) return string;
end mpis;
package body mpis is
-- formats string for reporting difference between expected and actual values
function format_diff( expected: integer; actual: integer) return string is
begin
return "expected " & integer'image(expected) & ", actual " & integer'image(actual);
end format_diff;
-- returns 'true' if both arguments represent the same number
function are_equal( vector: unsigned; number: natural) return boolean is
begin
return vector = to_unsigned(number, vector'length);
end are_equal;
function seven_segment_decoder( hex : unsigned(3 downto 0)) return std_logic_vector is
variable leds : std_logic_vector(6 downto 0);
begin
--
-- segment encoding
-- 0
-- ---
-- 5 | | 1
-- --- <- 6
-- 4 | | 2
-- ---
-- 3
case (hex) is
when "0000" =>
leds := "1000000"; --0
when "0001" =>
leds := "1111001"; --1
when "0010" =>
leds := "0100100"; --2
when "0011" =>
leds := "0110000"; --3
when "0100" =>
leds := "0011001"; --4
when "0101" =>
leds := "0010010"; --5
when "0110" =>
leds := "0000010"; --6
when "0111" =>
leds := "1111000"; --7
when "1000" =>
leds := "0000000"; --8
when "1001" =>
leds := "0010000"; --9
when "1010" =>
leds := "0001000"; -- A
when "1011" =>
leds := "0000011"; -- b
when "1100" =>
leds := "1000110"; -- C
when "1101" =>
leds := "0100001"; -- d
when "1110" =>
leds := "0000110"; -- E
when "1111" =>
leds := "0001110"; -- F
when others =>
leds := "1111111"; -- nothing
end case;
return leds;
end seven_segment_decoder;
end mpis;