Abstract: Methods and related structures for both operating and testing an integrated circuit constructed of combinations of customization logic and embedded cells. Functional modes include an operational mode and a test mode with two submodes. Test terminals of embedded cells, as well as test points in customization logic, are both accessed via a multiplexing scheme using test points of x-y (row and column) wiring traces of a grid-based "cross-check" test structure for both logic testing and embedded cell testing. Common conductors or traces can be used to operate the embedded cells and to control the made and test the embedded cells and customization logic. The x and y lines can be operated as signal lines, as probe lines, as sense lines and as control lines, as needed, using multiplexing according to the invention.