Spare Cells With Constant Insertion for Engineering Change
Yu-Min Kuo, Ya-Ting Chang, Shih-Chieh Chang, Malgorzata Marek-Sadowska · IEEE Transactions on Computer-Aided Design of Integrated Circuits and Systems · 2009
Engineering change (EC) is the process of modifying a VLSI design implementation to eliminate design errors, to add new specifications, or to correct design constraint violations. Usually, an EC problem is resolved by using spare cells that have been inserted into unused spaces on a chip. In this paper, we describe an iterative method to determine feasible mapping solutions for an EC problem considering spare cells whose inputs can be connected toVddorGnd. Setting some of the cell inputs to fixed values is referred to asconstantinsertion. Constant insertion can increase cells' functional flexibility. Our experimental results suggest that constant insertion reduces the area required to find a feasible mapping solution to 80% of that with no constant insertion for the selected EC equations. We also show a procedure for modifying the initial feasible EC solution such that the routing or timing improves.