module pass_thru_tb;
	reg clock;
	reg SDI, CSB, SCK, RSTB;
	reg power1, power2;

	wire gpio;
	wire [15:0] checkbits;
	wire [37:0] mprj_io;
	wire uart_tx;
	wire uart_rx;

	wire flash_csb;
	wire flash_clk;
	wire flash_io0;
	wire flash_io1;
	wire flash_io2;
	wire flash_io3;

	wire SDO;

	always #10 clock <= (clock === 1'b0);

	initial begin
		clock = 0;
	end

	initial begin		// Power-up sequence
		power1 <= 1'b0;
		power2 <= 1'b0;
		#200;
		power1 <= 1'b1;
		#200;
		power2 <= 1'b1;
	end

    // The main testbench is here.  Put the housekeeping SPI into
    // pass-thru mode and read several bytes from the flash SPI.

    // First define tasks for SPI functions

	task start_csb;
	    begin
		SCK <= 1'b0;
		SDI <= 1'b0;
		CSB <= 1'b0;
		#50;
	    end
	endtask

	task end_csb;
	    begin
		SCK <= 1'b0;
		SDI <= 1'b0;
		CSB <= 1'b1;
		#50;
	    end
	endtask

	task write_byte;
	    input [7:0] odata;
	    begin
		SCK <= 1'b0;
		for (i=7; i >= 0; i--) begin
		    #50;
		    SDI <= odata[i];
                    #50;
		    SCK <= 1'b1;
                    #100;
		    SCK <= 1'b0;
		end
	    end
	endtask

	task read_byte;
	    output [7:0] idata;
	    begin
		SCK <= 1'b0;
		SDI <= 1'b0;
		for (i=7; i >= 0; i--) begin
		    #50;
                    idata[i] = SDO;
                    #50;
		    SCK <= 1'b1;
                    #100;
		    SCK <= 1'b0;
		end
	    end
	endtask

	task read_write_byte
	    (input [7:0] odata,
	    output [7:0] idata);
	    begin
		SCK <= 1'b0;
		for (i=7; i >= 0; i--) begin
		    #50;
		    SDI <= odata[i];
                    idata[i] = SDO;
                    #50;
		    SCK <= 1'b1;
                    #100;
		    SCK <= 1'b0;
		end
	    end
	endtask
	
	integer i;

    // Now drive the digital signals on the housekeeping SPI
	reg [7:0] tbdata;

	initial begin
	    $dumpfile("pass_thru.vcd");
	    $dumpvars(0, pass_thru_tb);

	    CSB <= 1'b1;
	    SCK <= 1'b0;
	    SDI <= 1'b0;
	    RSTB <= 1'b0;

	    #2000;

	    RSTB <= 1'b1;

	    // Wait on start of program execution
	    wait(checkbits == 16'hA000);

            // First do a normal read from the housekeeping SPI to
	    // make sure the housekeeping SPI works.

	    start_csb();
	    write_byte(8'h40);	// Read stream command
	    write_byte(8'h03);	// Address (register 3 = product ID)
	    read_byte(tbdata);
	    end_csb();
	    #10;
	    $display("Read data = 0x%02x (should be 0x10)", tbdata);
	    if(tbdata !== 8'h10) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end

	    start_csb();
	    write_byte(8'hc4);	// Pass-thru mode
	    write_byte(8'h03);	// Command 03 (read values w/3-byte address
	    write_byte(8'h00);	// Address is next three bytes (0x000000)
	    write_byte(8'h00);
	    write_byte(8'h00);

	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x93)", tbdata);
	    if(tbdata !== 8'h93) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x00)", tbdata);
	    if(tbdata !== 8'h00) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x00)", tbdata);
	    if(tbdata !== 8'h00) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x00)", tbdata);
	    if(tbdata !== 8'h00) begin
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x93)", tbdata);
	    if(tbdata !== 8'h93) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x01)", tbdata);
	    if(tbdata !== 8'h01) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x00)", tbdata);
	    if(tbdata !== 8'h00) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end
	    read_byte(tbdata);
	    $display("Read flash data = 0x%02x (should be 0x00)", tbdata);
	    if(tbdata !== 8'h00) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end

	    end_csb();

	    // Wait for processor to restart
	    wait(checkbits == 16'hA000);

	    // Read product ID register again

	    start_csb();
	    write_byte(8'h40);	// Read stream command
	    write_byte(8'h03);	// Address (register 3 = product ID)
	    read_byte(tbdata);
	    end_csb();
	    #10;
	    $display("Read data = 0x%02x (should be 0x10)", tbdata);
	    if(tbdata !== 8'h10) begin 
			`ifdef GL
				$display("Monitor: Test HK SPI Pass-thru (GL) Failed"); $finish; 
			`else
				$display("Monitor: Test HK SPI Pass-thru (RTL) Failed"); $finish; 
			`endif
		end

		`ifdef GL
	    	$display("Monitor: Test HK SPI Pass-thru (GL) Passed");
		`else
			$display("Monitor: Test HK SPI Pass-thru (RTL) Passed");
		`endif
		
	    #10000;
 	    $finish;
	end

	wire VDD3V3;
	wire VDD1V8;
	wire VSS;

	assign VDD3V3 = power1;
	assign VDD1V8 = power2;
	assign VSS = 1'b0;

	wire hk_sck;
	wire hk_csb;
	wire hk_sdi;

	assign hk_sck = SCK;
	assign hk_csb = CSB;
	assign hk_sdi = SDI;

	assign checkbits = mprj_io[31:16];
	assign uart_tx = mprj_io[6];
	assign mprj_io[5] = uart_rx;
	assign mprj_io[4] = hk_sck;
	assign mprj_io[3] = hk_csb;
	assign mprj_io[2] = hk_sdi;
	assign SDO = mprj_io[1];
	
	caravel uut (
		.vddio	  (VDD3V3),
		.vssio	  (VSS),
		.vdda	  (VDD3V3),
		.vssa	  (VSS),
		.vccd	  (VDD1V8),
		.vssd	  (VSS),
		.vdda1    (VDD3V3),
		.vdda2    (VDD3V3),
		.vssa1	  (VSS),
		.vssa2	  (VSS),
		.vccd1	  (VDD1V8),
		.vccd2	  (VDD1V8),
		.vssd1	  (VSS),
		.vssd2	  (VSS),
		.clock	  (clock),
		.gpio     (gpio),
		.mprj_io  (mprj_io),
		.flash_csb(flash_csb),
		.flash_clk(flash_clk),
		.flash_io0(flash_io0),
		.flash_io1(flash_io1),
		.resetb	  (RSTB)
	);

	spiflash #(
		.FILENAME("pass_thru.hex")
	) spiflash (
		.csb(flash_csb),
		.clk(flash_clk),
		.io0(flash_io0),
		.io1(flash_io1),
		.io2(),			// not used
		.io3()			// not used
	);

	tbuart tbuart (
		.ser_rx(uart_tx)
	);
		
endmodule