Using the boundary scan delay chain for cross-chip delay measurement and characterization of delay modeling flow

Abstract

For ASICs/SOCs/lCs it is often very important to have an easily accessible delay measurements path for several reasons. The delay of a long path running across the whole chip through lots of instances (inverters, MUXes) makes it possible to measure the final process parameters of an ASIC/IC within the best and worst case production process window. This information is very important for production testing and assembly at the vendor site. But very often this information is also necessary at circuit pack level, system test level and even in the field - when in the case of problems (functionality, timing, debugging) it should be known which "quality level" the ASIC/IC device has reached. Also for characterization of the delay modeling during the different design phases (estimation, floorplanning, trial and final layout) such a dedicated delay path may help in qualifying the delay models. We propose to use a new standard methodology to address these issues by definition of a dedicated delay path. It is called "Boundary Scan Delay Chain" (BSDC). We use the Boundary Scan data register according to IEEE1149.1 to get a delay chain across the chip. Only a slight modification of the boundary scan cell (e.g. BC 1, BC 4) is necessary. The resulting new functionality still conforms to IEEE1149.1.