9086/cpu/testbench.v

`timescale 1ns/1ps

module tb;
wire clock;
reg reset;
reg  clk_enable;
wire [19:0]address_bus;
wire [15:0]data_bus;
wire rd,wr,romcs,HALT;
wire ERROR;

processor p(clock,reset,address_bus,data_bus,rd,wr,HALT,ERROR);
rom bootrom(address_bus,data_bus,rd,romcs);

`define CPU_SPEED 1000

clock_gen #(.FREQ(1000)) u1(clk_enable, clock);

assign romcs=0;
integer cycles=0;

initial begin
	$dumpfile("test.lx2");
	$dumpvars(0,p,u1);
	reset = 0;
	clk_enable <= 1;

	#($random%500)
	#(`CPU_SPEED) 
	reset = 1;
end

always @(posedge HALT) begin
	$display("Processor halted.\nCycles run for: %d",cycles);
	$writememh("memdump.txt", bootrom.memory);
	#(`CPU_SPEED) //Just for the waveform
	$finish;
end

always @(posedge ERROR) begin
	clk_enable <= 0;
	$display("PROCESSOR RUN INTO AN ERROR.\nCycles run for: %d",cycles);
	$writememh("memdump.txt", bootrom.memory);
	#(`CPU_SPEED) //Just for the waveform
	$finish;
end

always @(posedge clock)begin
	if(reset==1)
		cycles=cycles+1;
end

endmodule


/*Clock generator*/
module clock_gen (input enable, output reg clk);

parameter FREQ = 1000;  // in HZ
parameter PHASE = 0;    // in degrees
parameter DUTY = 50;    // in percentage 

real clk_pd	= 1.0/FREQ * 1000000; 	// convert to ms
real clk_on	= DUTY/100.0 * clk_pd;
real clk_off	= (100.0 - DUTY)/100.0 * clk_pd;
real quarter	= clk_pd/4;
real start_dly	= quarter * PHASE/90;

reg start_clk;

initial begin
end

// Initialize variables to zero
initial begin
	clk <= 0;
	start_clk <= 0;
end

// When clock is enabled, delay driving the clock to one in order
// to achieve the phase effect. start_dly is configured to the 
// correct delay for the configured phase. When enable is 0,
// allow enough time to complete the current clock period
always @ (posedge enable or negedge enable) begin
	if (enable) begin
		#(start_dly) start_clk = 1;
	end else begin
		#(start_dly) start_clk = 0;
	end      
end

// Achieve duty cycle by a skewed clock on/off time and let this
// run as long as the clocks are turned on.
always @(posedge start_clk) begin
	if (start_clk) begin
		clk = 1;

		while (start_clk) begin
			#(clk_on)  clk = 0;
			#(clk_off) clk = 1;
		end

		clk = 0;
	end
end 
endmodule