Simple Telephone Conversation on Fpga board and SSD

Hello,

Ä° have a code like this and i have to use SSD for outputs.

module telephoneConversation(clock, reset, caller, callee, areaCode, startEnd, letter, display, leds);

input clock, reset, caller,callee;
input areaCode; // 0: city_A, 1: city_B
input startEnd; // 0: start, 1: end
input [2:0] letter; // a character (from the code) of 3 bits
output reg [27:0] display; // 4 displays of each 7 bits
output reg [7:0] leds; // represents the correctness of the guess

reg [3:0] current_state; // current state of the circuitry
reg [3:0] next_state; // next state of the circuitry
reg [14:0] characterCount; // number of characters transferred
reg [12:0] transitionCounter; // counter to wait in the states
reg [1:0] areaCode_caller;
reg [1:0] areaCode_callee;
… // additional registers

// sequential part - state transitions
always @ (posedge clk or posedge rst)
begin
…
end

// combinational part - next state definitions
always @ (*)
begin
…
end

// sequential part - control registers
always @ (posedge clk or posedge rst)
begin
…
end

// sequential part - outputs
always @ (posedge clk or posedge rst)
begin
…
end

…

endmodule

I have a ssd code like this

"`timescale 1ns / 1ps
//////////////////////////////////////////////////////////////////////////////////
// Company:
// Engineer:
//
// Create Date: 19:32:18 01/04/2010
// Design Name:
// Module Name: ssd
// Project Name:
// Target Devices:
// Tool versions:
// Description: This module drives the seven segment displays. It has got 4 different inputs
// for the 4 digits on the board. It's inputs are not directly the binary numbers.
// You need to convert 4-bit hex values to their seven segment display equivalents.
//
// a0,b0,c0,d0,e0,f0,g0 belongs to digit0, rigth most digit on the board.
// a1,b1,c1,d1,e1,f1,g1 belongs to digit1, 2. from the rigth digit on the board.
// a2,b2,c2,d2,e2,f2,g2 belongs to digit2, 3. from the rigth digit on the board.
// a3,b3,c3,d3,e3,f3,g3 belongs to digit3, left most digit on the board.
//
// The values that you connect to these inputs will appear on the display digits.
// Thus, you just need to make the appropriate connections and should not concern
// about the rest.
//
// Dependencies:
//
// Revision:
// Revision 0.01 - File Created
// Additional Comments:
//
//////////////////////////////////////////////////////////////////////////////////
module ssd( clk, reset, a0,a1,a2,a3,b0,b1,b2,b3,c0,c1,c2,c3,d0,d1,d2,d3,e0,e1,e2,e3,
f0,f1,f2,f3,g0,g1,g2,g3,a,b,c,d,e,f,g,an0,an1,an2,an3
);

input clk, reset;// set clock and reset as input(1 bit)
input a0,a1,a2,a3,b0,b1,b2,b3,c0,c1,c2,c3,d0,d1,d2,d3,e0,e1,e2,e3,f0,f1,f2,f3,g0,g1,g2,g3;//set our display data as input(1 bit)
output reg a,b,c,d,e,f,g,an0,an1,an2,an3;//set outputs also as registers (1 bit)

reg [2:0] state;//holds state number (3 bit)
reg [14:0] counter;//counter to slow the input clock(15 bit)

//in this always block the speed of the clock reduced by 25000 times so that display works properly
always @ (posedge clk) begin //state counter
if(reset) begin //synchronus reset
state <= 0; //if reset set state and counter to zero
counter <= 0;
end else begin //else the counter untill 25000

if(counter == 15'h61A8) begin //if equal to 25000
if (state == 3'b100) //if it is in the last state return to state 1
state <= 1;
else //else go one state up
state <= state + 1;

counter <= 0; //0 the counter because after it reaches 25000
end
else
counter <= counter + 1; //if not 25000 add 1
end
end
//in this always block we give the inputs to the leds by choosing
//different display segment in each time
//!(In the button-pin sheet of the Basys, the 7-SEG numbers are assinged wrong.
//To avoid confusion we corrected it while choosing an0,an1... So if you just enter
//pin numbers according to the sheet it will work fine.)
always@(posedge clk)
begin
if(reset)// if reset initilize the outputs
begin
an0 <= 1;
an1 <= 1;
an2 <= 1;
an3 <= 1;
a <= 1;
b <= 1;
c <= 1;
d <= 1;
e <= 1;
f <= 1;
g <= 1;
end
else if(state == 3'b001) //state 1 gives the led outputs to the AN0
begin
an0 <= 1;
an1 <= 1;
an2 <= 1;
an3 <= 0;
a <= a0;
b <= b0;
c <= c0;
d <= d0;
e <= e0;
f <= f0;
g <= g0;
end
else if(state == 3'b010) //state 2 gives the led outputs to the AN1
begin
an0 <= 0;
an1 <= 1;
an2 <= 1;
an3 <= 1;
a <= a1;
b <= b1;
c <= c1;
d <= d1;
e <= e1;
f <= f1;
g <= g1;
end
else if(state == 3'b011) //state 3 gives the led outputs to the AN2
begin
an0 <= 1;
an1 <= 0;
an2 <= 1;
an3 <= 1;
a <= a2;
b <= b2;
c <= c2;
d <= d2;
e <= e2;
f <= f2;
g <= g2;
end
else if(state == 3'b100) //state 4 gives the led outputs to the AN3
begin
an0 <= 1;
an1 <= 1;
an2 <= 0;
an3 <= 1;
a <= a3;
b <= b3;
c <= c3;
d <= d3;
e <= e3;
f <= f3;
g <= g3;
end
else //For other states default inputs and outputs
begin
an0 <= 1;
an1 <= 1;
an2 <= 1;
an3 <= 1;
a <= 1;
b <= 1;
c <= 1;
d <= 1;
e <= 1;
f <= 1;
g <= 1;
end
end
endmodule
"

how can i use ssd.v file in main file. How can i call functions. Where should i do convert 4-bit hex values to their seven segment display equivalents?