Vending machine

This is a sample of my FSM code where e pretend to make te change(troco in the code)

"total" is the sum of the total of the coins

library IEEE;

use IEEe.STD_LOGIC_UNSIGNED.all;

use IEEE.STD_LOGIC_1164.all;

use IEEE.NUMERIC_STD.all;

entity VendingMachine is

port(sel: in std_logic_vector(1 downto 0);

reset,clk,u,d,c,t: in std_logic;

drink: out std_logic;

total: out std_logic_vector(7 downto 0);

troco: out std_logic_vector(7 downto 0));

end VendingMachine;

architecture Behav of VendingMachine is

type estados is(s0, s10,s20,s30,s40,s50,s60,s70,s80,s90,s100,s110,s120,s130,s140,s150,s160,s170,s180,s190,s200,s210,opnd);

signal ps, ns : estados;

signal s_preco : std_logic_vector ( 7 downto 0);

signal s_troco: std_logic_vector(7 downto 0);

begin

roms: work.ROM_Venda(RTL)

port map(dataOut => s_preco,

address => sel);

sync_proc: process(clk, reset)

begin

if(reset = '1') then

ps <= s0;

elsif(rising_edge(clk)) then

ps <= ns;

end if;

end process;

comb_proc: process(ps,u,d,c,t,ns)

begin

ns <= ps;

case ps is

when s0 => --0.00€

if u = '1' then ns <= s10;

elsif d = '1' then ns <= s20;

elsif c = '1' then ns <= s50;

elsif t = '1' then ns <= s100;

end if;

total <="00000000";

when s10 =>

if u = '1' then ns <= s20;

elsif d = '1' then ns <= s30;

elsif c = '1' then ns <= s60;

elsif t = '1' then ns <= s110;

end if;

total <="00001010";

troco <= s_preco(0) - total;