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Download ASIC/IC Design-For-Test Process Guide
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Understanding Common Tool Terminology and Concepts Scan Terminology Shadow Element The shadow element, either dependently- or independently-clocked, resides outside the scan chain path. Figure 3-5 gives an example of a scan cell with an independently-clocked, nonobservable shadow element with a non-inverted value. sys_clk Master Element clk data sc_in sc_en FF MUX S FF Shadow Element sc_out Figure 3-5. Mux-DFF/Shadow Element Example You load a data value into the shadow element with either the shift procedure or, if independently clocked, with a separate procedure called shadow_control. You can optionally make a shadow observable using the shadow_observe procedure. A scan cell may contain multiple shadows but only one may be observable, because the tools allow only one shadow_observe procedure. A shadow element’s value may be the inverse of the master’s value. ASIC/IC Design-for-Test Process Guide, V8.6_1 December 1997 3-5
