`timescale 1ns/1ns

module LIFO(
  reset,
  push,
  pop,
  push_data,
  pop_data,
  stack_empty,
  stack_full
);

parameter LIFO_WIDTH = 8;
parameter LIFO_DEPTH = 16;

input   reset; // async reset, active on 1
input   push;  // push
input   pop;   // pop
input   [LIFO_WIDTH-1:0] push_data;
output  [LIFO_WIDTH-1:0] pop_data;
output  stack_empty;
output  stack_full;

// interface
wire   reset;
wire   push; // push request
wire   pop; //  pop request
wire   [LIFO_WIDTH-1:0] push_data;
reg    [LIFO_WIDTH-1:0]   pop_data;
reg    stack_empty;
reg    stack_full;

// internals
reg [LIFO_WIDTH-1:0] lifo[LIFO_DEPTH-1:0];  
reg [LIFO_WIDTH-1:0] stack_ptr;
integer i;

always @ (reset or stack_ptr) 
  begin
   if (reset==1) stack_ptr = 0;
   case (stack_ptr) 
       0: stack_empty = 1'b1;
       LIFO_DEPTH: begin
                     $display("Lifo full\n"); 
                     stack_full = 1'b1;
                   end
       default: begin
                $display("Default reached\n");
                stack_empty = 1'b0;
                stack_full = 1'b0;
                end
  endcase
  end



always @ (posedge push or posedge pop) 
  begin
     if ( pop == 1'b1 ) // pop  
       begin
	 stack_ptr = stack_ptr - 1; 
         pop_data = lifo[stack_ptr];
         $display("stack_ptr=%x, pop_data=%x\n",stack_ptr, pop_data);
       end
     else if (push == 1'b1) // push  
       begin
    	   lifo[stack_ptr] = push_data; 
           stack_ptr = stack_ptr + 1; 
           $display("Pushed data=0x%x, lifo[stack_ptr]=0x%x\n", push_data, lifo[stack_ptr]);
           for (i = 0; i < LIFO_DEPTH ; i = i + 1) $display("lifo[%d]=0x%x, stack_ptr=0x%x\n", i, lifo[i], stack_ptr);
       end
    end

endmodule