Abstract: A phase comparator compares phase of a clock signal and a generated comparison clock signal based upon rising edges. The output of the phase comparator may include a series of short up (U) pulses or down (D) pulses, depending whether the phase of the comparison clock is leading or lagging the clock. Up and down pulses U and D control an up/down shift register which in turn compensates phase difference by inserting or removing additional discrete delay elements in a variable delay line. Based upon delay signals generated by the variable delay line, a double frequency clock generator generates a 2.times. clock signal. The 2.times. clock signal is divided by 2 in a divider to supply the phase comparator with the generated comparison clock signal. The feedback scheme helps the digital delay lock loop of stabilize after a few clock cycles without additional external control.

Abstract: A method and system to efficiently incorporate engineering change order (ECO) modifications into an integrated circuit layout having configurable gate array cells is provided. In generating the original integrated circuit layout, extra gate array cells are inserted into the layout. These gate array cells can be reconfigured to modify their functionality according to changes specified by the ECO. A new netlist with a description of the required modifications is generated and provided to a place-and-route CAD tool to create a new layout of the integrated circuit.