88 lines
2.3 KiB
VHDL
88 lines
2.3 KiB
VHDL
library ieee;
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use ieee.std_logic_1164.all;
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use ieee.std_logic_unsigned.all;
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use ieee.numeric_std.all;
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use std.textio.all;
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use ieee.std_logic_textio.all;
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entity font_rom is
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generic (
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input_clk: integer
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);
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port (
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clk: in std_logic;
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x, y: in std_logic_vector(9 downto 0);
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rgb: out std_logic_vector(23 downto 0)
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);
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end font_rom;
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architecture logic of font_rom is
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type rom_type is array(0 to 127) of std_logic_vector(63 downto 0);
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type framebuffer_type is array(0 to 59, 0 to 79) of std_logic_vector(7 downto 0);
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impure function read_font(filename: in string) return rom_type is
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file rom_file: text is in filename;
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variable rom_line: line;
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variable rom: rom_type;
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begin
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-- skip comment in first line
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readline(rom_file, rom_line);
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for i in rom_type'range loop
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readline(rom_file, rom_line);
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hread(rom_line, rom(i));
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end loop;
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return rom;
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end function;
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constant font: rom_type := read_font("font.hex");
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constant framebuffer: framebuffer_type := (
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0 => (x"48", x"61", x"6C", x"6c", x"6f", others => x"00"),
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1 to 59 => (others => x"00")
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);
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signal char_x: integer range 0 to 79;
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signal char_y: integer range 0 to 59;
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signal current_char: std_logic_vector(7 downto 0);
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signal current_glyph: std_logic_vector(63 downto 0);
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signal current_glyph_pos: integer range 0 to 127;
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signal glyph_pos_raw: std_logic_vector(5 downto 0);
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signal glyph_pos: integer range 0 to 63;
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begin
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char_x <= to_integer(unsigned(x(9 downto 3)));
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char_y <= to_integer(unsigned(y(9 downto 3)));
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process(clk) is
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begin
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if rising_edge(clk) then
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current_char <= framebuffer(char_y, char_x);
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end if;
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end process;
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current_glyph_pos <= to_integer(unsigned(current_char));
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process(clk) is
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begin
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if rising_edge(clk) then
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current_glyph <= font(current_glyph_pos);
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end if;
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end process;
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glyph_pos_raw <= y(2 downto 0) & x(2 downto 0);
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glyph_pos <= to_integer(unsigned(glyph_pos_raw));
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-- actually currently BRG
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rgb <=
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"111111111111111111111111" when current_glyph(glyph_pos) = '1' else
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"000000000000000000000000";
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end logic;
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