diff --git a/dvi.v b/dvi.v
index 808865b..f4b31c6 100644
--- a/dvi.v
+++ b/dvi.v
@@ -119,8 +119,8 @@ module dvi #(
 	end
 
 	always @(negedge bus_clk) begin
-		if (output_state == OUTPUT_IDLE) ck <= 0;
-		else                             ck <= ~ck;
+		if (output_state == OUTPUT_IDLE || ck == 1) ck <= 0;
+		else                                        ck <= 1;
 
 		if (y == 11'b0) begin
 			bus_addr <= BASE_ADDR;