Vending machine

[Altera_Forum]

Hello guys. I have a school project, that consists in making a Vending Machine with 3 products and we can only use 4 types of coins. My machine has to make change, and i don't know how to do it and i could use some help. So far i've done a FSM for the coins and a ROM with the value of the products.

[Altera_Forum]

this is my ROM code 

library IEEE; use IEEE.STD_LOGIC_1164.all; use IEEE.NUMERIC_STD.all;   entity ROM_Venda is  port(address : in std_logic_vector(1 downto 0);  dataOut : out std_logic_vector(7 downto 0)); end ROM_Venda;   architecture RTL of ROM_Venda is    subtype TDataWord is std_logic_vector(7 downto 0);  type TROM is array(0 to 3) of TDataWord;    constant c_memory: TROM := (0 =>"00000000", 1 =>"01010000", 2=>"01100100", 3=> "01111000"); -- Produto 1 ->80 Produto 2 ->100 Produto 3 ->120   begin  process (address)  begin   case address is   when "00" =>  dataOut <= c_memory(0);  when "01" =>   dataOut <= c_memory(1);  when "10" =>  dataOut <= c_memory(2);  when "11" =>  dataOut <= c_memory(3);  end case;   end process;  end RTL;

[Altera_Forum]

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;

[Altera_Forum]

isn't this a duplicate of http://www.alteraforum.com/forum/showthread.php?t=52393, which you have started as well? 

What's different?

[Altera_Forum]

The problem now is making change using the values in the ROM...

[Altera_Forum]

Ok, what have you done? I don' see any ROM code here. And by making change I assume you mean change in coins?