Abstract: An improved method and apparatus for altering the effective electrical length of trace on a circuit board. In the present invention small tabs of etch are routed perpendicular to the trace in the unused areas between adjacent traces. In an embodiment of the invention, a method of tuning the delay characteristics of a transmission line is implemented by inserting compensation tabs into the unused area between the segments of adjacent straight traces or a serpentine run. Utilizing the method and apparatus of the present invention, it is possible to achieve significantly greater electrical length for an electrical trace without introducing coupling problems or utilizing large amounts of space on a circuit board.

Abstract: An adaptive reference voltage method and system analyzes a received bus signal to evaluate voltage swing characteristics and adjusts the reference voltage for reading the signal to a level that compensates for variations in margins between high and low signal switching values such as are introduced by noise. A bus input signal analyzer circuit incorporated in an integrated circuit analyzes the bus signal received at the integrated circuit to adjust the reference voltage used by the integrated circuit. In one embodiment, the bus input signal analyzer circuit applies a feedback loop to adapt the reference voltage by setting high and low input values to a reference voltage generation circuit with the reference voltage centered between the high and low values, such as results from a resistor divider network.

Abstract: An adaptive reference voltage method and system analyzes a received bus signal to evaluate voltage swing characteristics and adjusts the reference voltage for reading the signal to a level that compensates for variations in margins between high and low signal switching values such as are introduced by noise. A bus input signal analyzer circuit incorporated in an integrated circuit analyzes the bus signal received at the integrated circuit to adjust the reference voltage used by the integrated circuit. In one embodiment, the bus input signal analyzer circuit applies a feedback loop to adapt the reference voltage by setting high and low input values to a reference voltage generation circuit with the reference voltage centered between the high and low values, such as results from a resistor divider network.

Abstract: Disclosed are an apparatus and method preferably for testing personal computer (PC) bus transmission line characteristics. The apparatus comprises: (1) a plurality of transmission line segments having different physical dimensions, each of the plurality of segments having a different electrical effect on signals transmitted thereon and (2) a switching circuit capable of coupling successive ones of the plurality of segments to an external conductor, an electrical characteristic of the external conductor affected by the coupling of the successive ones of the plurality of segments thereto, the apparatus permitting signals to pass through the external conductor and a selected one of the plurality of segments via the switching circuit. The apparatus allows a determination of a susceptibility of the external conductor to changes in transmission line electrical characteristics brought about by various possible combinations of peripheral expansion bus cards.