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//
// This reference design file, and your use thereof, is subject to and governed
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/////////////////////////////////////////////////////////////////////////////

// baeckler - 12-18-2008

module twenty_to_eight_tb ();

parameter WORD_LEN = 16;

reg clk,arst;

reg [8*WORD_LEN-1:0] din = 0;
reg din_valid;
wire din_ready;

wire [20*WORD_LEN-1:0] middle;
wire middle_valid,middle_ready;

wire [8*WORD_LEN-1:0] dout;
wire dout_valid;
reg dout_ready;
	
eight_to_twenty #(
	.WORD_LEN(WORD_LEN)
)
dut_8_20
(
	.clk,.arst,
	
	.din, 
	.din_valid,
	.din_ready,
	
	.dout(middle),
	.dout_ready(middle_ready),
	.dout_valid(middle_valid)		
);

twenty_to_eight #(
	.WORD_LEN(WORD_LEN)
)
dut_20_8
(
	.clk,.arst,
	
	.din(middle),
	.din_valid(middle_valid),
	.din_ready(middle_ready),
	
	.dout,
	.dout_ready,
	.dout_valid
);

// readback + verify
reg fail = 0;
integer k;
reg [8*WORD_LEN-1:0] check;
reg [WORD_LEN-1:0] exp = 1;
always @(posedge clk) begin
	if (dout_valid & dout_ready) begin
		check = dout;
		for (k=0; k<8; k=k+1) begin
			if (check[WORD_LEN-1:0] != 0) begin
				if (exp != check[WORD_LEN-1:0]) begin
					$display ("Mismatch at time %d",$time);
					fail = 1;
				end
				exp = exp + 1;
			end
			check = check >> WORD_LEN;
		end
	end
end

reg last_din_valid, last_din_ready;
always @(posedge clk) begin
	last_din_valid <= din_valid;
	last_din_ready <= din_ready;
end

// test stimulus
integer n;
reg [WORD_LEN-1:0] tmp = 0;
always @(negedge clk) begin
	din_valid = $random;
	dout_ready = $random;
	if (last_din_valid & last_din_ready) begin
		for (n=0; n<8; n=n+1) begin
			tmp = tmp + 1;
			din = (din >> WORD_LEN) | (tmp << 7*WORD_LEN);	
		end
	end
end

initial begin
	clk = 0; 
	arst = 0;
	#1 arst = 1;
	@(negedge clk) arst = 0;
end

always begin
	#5 clk = ~clk;
end

endmodule