Design of VHDL telephone billing system

Telephone billing system ,

Implemented function ：
Use the key to simulate on or off , stay 1602 Display the call time and consumption amount on the , Consumption is subject to one minute The duration of each call reaches 1 Charge will be deducted every minute . When the balance is insufficient, it will remind .

The design uses VHDL Language .

Use quartus Create project under ：

The system displays the design code ：

LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.std_logic_unsigned.all;

ENTITY lcd14432 IS
PORT (
nreset : IN STD_LOGIC;
clk_in : IN STD_LOGIC;
LCD_RS : OUT STD_LOGIC;
LCD_RW : OUT STD_LOGIC;
LCD_EN : OUT STD_LOGIC;
LCD_Data : OUT STD_LOGIC_VECTOR(7 DOWNTO 0);
LED :IN STD_LOGIC_VECTOR(15 DOWNTO 0);
F :IN STD_LOGIC:=‘0’;-------------- Press the key to press the flag bit
FLAG1 :IN STD_LOGIC:=‘0’;--------- Password input success flag bit
FLAG2 :IN STD_LOGIC:=‘0’;-------- Key on flag bit
miaog,miaos,feng,fens,shig,shis:IN STD_LOGIC_VECTOR(3 DOWNTO 0);
FLAG4 :IN STD_LOGIC:=‘0’;------------- Balance display flag bit
MONEY1 :IN STD_LOGIC_VECTOR