Boundary scan chain routing

A system, comprising:

• a substrate;
• a plurality of integrated circuits mounted on the substrate;
• a plurality of scan cells, each scan cell capable of implementing scan functions associated with one of the plurality of integrated circuits, each scan cell having a TDI input and a TDO output, the plurality of scan cells structured as a shift register to shift data from one integrated circuit in a direction unilaterally to an adjacent integrated circuit, one of the plurality of integrated circuits being a first integrated circuit defined as the first of the plurality of integrated circuits to receive data, one of the plurality of integrated circuits being a last integrated circuits defined as the last of the plurality of integrated circuits to receive data;
• an endless control conductor forming a loop proximate the plurality of integrated circuits, the endless control conductor coupled to each of the plurality of integrated circuits for conducting a test clock signal to each of the plurality of integrated circuits;
• and
• at least one other control conductor extending around the substrate proximate the plurality of integrated circuits, the at least one other control conductor coupled to each of the plurality of integrated circuits, the at least one other control conductor discontinuous between the first and last integrated circuits.

A method of controlling a scan system, comprising:

• Implementing, in a plurality of scan cells, boundary scan functions associated with one of the plurality of input/output pads, each scan cell having a TDI input and a TDO output, the plurality of boundary scan cells structured as a shift register to shift data from one boundary scan cell in a direction unilaterally to an adjacent boundary scan cell, one of the plurality of boundary scan cells being a first boundary scan cell defined as the first of the plurality of scan cells to receive data, one of the plurality of scan cells being a last boundary scan cell defined as the last of the plurality of scan cells to receive data;
• routing an endless control conductor forming a loop proximate the plurality of scan cells;
• coupling the endless control conductor to each of the plurality of scan cells for conducting a test clock signal to each of the plurality of scan cells;
• and
• routing at least one other control conductor proximate the plurality of scan cells, the at least one other control conductor coupled to each of the plurality of scan cells, the at least one other control conductor discontinuous between the first and last scan cells.