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library ieee;
use ieee.std_logic_1164.all;
use ieee.numeric_std.all;
use work.read_intel_hex_pack.all;
entity tb_pic is
end entity tb_pic;
architecture behavioural of tb_pic is
constant T_clk : time := 20 ns; -- 50M
constant HEX_FILE : string := "program.hex";
constant SIM_CYCLES : integer := 800_000;
signal clk : std_logic := '0';
signal reset : std_logic := '1';
signal opcode : std_logic_vector(13 downto 0);
signal program_counter : std_logic_vector(12 downto 0);
signal instruction_return : std_logic;
signal work_reg : std_logic_vector(7 downto 0);
signal status : std_logic_vector(2 downto 0);
signal port_a : std_logic_vector(7 downto 0);
signal port_b : std_logic_vector(7 downto 0);
signal done : boolean := false;
signal uart_tx : std_logic;
signal uart_rx : std_logic := '1'; -- idle high (no incoming bytes)
-- program memory: 1024 x 14-bit
signal prog_mem : program_array := (others => (others => '0'));
begin
clk <= not clk after T_clk / 2 when not done else unaffected;
-- drive opcode from program memory using PC
opcode <= prog_mem(to_integer(unsigned(program_counter)));
dut : entity work.PIC(rtl)
generic map (
CLK_FREQ => 50_000_000 -- 10 MHz, matches T_clk = 100 ns
)
port map (
clk => clk,
reset => reset,
opcode => opcode,
program_counter => program_counter,
instruction_return => instruction_return,
work_reg => work_reg,
status => status,
port_a => port_a,
port_b => port_b,
uart_tx => uart_tx,
uart_rx => uart_rx
);
stimulus : process is
variable mem : program_array;
begin
-- load hex file into program memory
read_ihex_file(HEX_FILE, mem);
prog_mem <= mem;
-- reset pulse
reset <= '1';
wait for T_clk * 2;
reset <= '0';
-- run for SIM_CYCLES instruction cycles
for i in 0 to SIM_CYCLES - 1 loop
wait until rising_edge(clk);
end loop;
report "simulation done. port_a=" & integer'image(to_integer(unsigned(port_a)))
& " port_b=" & integer'image(to_integer(unsigned(port_b)))
severity note;
done <= true;
wait;
end process stimulus;
end architecture behavioural;
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