`timescale 1 ns/1 ns
 
module CTP_LTU_emu(
	input clk,
	input reset,
	input BUSY,
	input LM_SA,
	output reg LM_GL,
	output reg TTC_A);

	reg [2:0] state;
	reg clk_fast;
	
	integer 
		GSrec,
		LMsent,
		L0sent,
		L1sent;
		
	integer counter;
	
	parameter
		GroundState = 3'b000,
		LevelM = 3'b001,
		Level0 = 3'b010,
		Level1 = 3'b011,
		standalone = 3'b100,
		standalone_0 = 3'b110,
		standalone_1 = 3'b111;

	initial begin
		LM_GL <= 0;
		TTC_A <= 0;
		state <= 0;
		clk_fast <= 0;
		counter <= 0;
	end
	
	always begin
		#1 clk_fast <= !clk_fast;
	end

	always @(posedge LM_SA) begin
		state = standalone_0;
		LM_GL <= 0;
		TTC_A <= 0;
		counter <= 0;
	end
	
	always @(clk_fast) begin
		if (reset == 1) begin
			state <= GroundState;
			counter <= 0;
			LM_GL <= 0;
			TTC_A <= 0;
		end
		else begin
			if (counter == 0) begin
				case (state)
					GroundState: begin
						if (BUSY == 0) begin
							GSrec <= $time;
							state <= LevelM;
							counter = $urandom_range(500,5);
						end
					end
					LevelM: begin
						LMsent <= $time;
						state <= Level0;
						counter = 300;//$urandom_range(305,245);
						if (counter > 300)
							$display("%t ns: L0 will arrive too late", $time/1000.0);
						if (counter < 250)
							$display("%t ns: L0 will arrive too early", $time/1000.0);
						LM_GL <= 1;
						#25 LM_GL <= 0;
					end
					Level0: begin
						L0sent <= $time;
						state <= Level1;
						counter = 5300;//$urandom_range(5305,5245);
						if (counter > 5300)
							$display("%t ns: L1 will arrive too late", $time/1000.0);
						if (counter < 5250)
							$display("%t ns: L1 will arrive too early", $time/1000.0);
						TTC_A <= 1;
						#25 TTC_A <= 0;
					end
					Level1: begin
						L1sent <= $time;
						state <= GroundState;
						TTC_A <= 1;
						#50 TTC_A <= 0;
						// $display("%t: Normal mode:", $time);
						// $display("Gs->LM: %t, LM: ",LMsent-GSrec, LMsent);
						// $display("LM->L0: %t, L0: ",L0sent-LMsent, L0sent);
						// $display("L0->L1: %t, L1:",L1sent-L0sent, L1sent);
						// $display("");
					end
					standalone_0: begin
						L0sent <= $time;
						state <= standalone_1;
						counter = 5270;//$urandom_range(5285,5265);	// 5300ns - 25ns (L0-Signal) +- 5ns (spare) +- 5ns (errors) = 5285/5265ns
						TTC_A <= 1;
						#25 TTC_A <= 0;
					end
					standalone_1: begin
						L1sent <= $time;
						state <= GroundState;
						TTC_A <= 1;
						#50 TTC_A <= 0;
						// $display("Standalone mode:");
						// $display("Gs->LM: ",LMsent-GSrec);
						// $display("LM->L0: ",L0sent-LMsent);
						// $display("L0->L1: ",L1sent-L0sent);
						// $display("");
					end
				endcase
			end
			else begin
				counter <= counter - 1;
			end
		end
	end
endmodule