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3.5 A Complete Analytical FPGA Power Mod... > 3.5.2 Exploration Phase: Locating Sp... - Pg. 60

60 CHAPTER 3 Power Estimation in FPGAs 3.5.2 Exploration Phase: Locating Spatial Correlation Spatial correlation among signals in VLSI circuits occurs whenever two signals are correlated. Correlations arise when two or more signals share a common driver or a com- mon parent logic block (x) and are connected as inputs to another logic block (y), i.e., reconvergent paths. If the cir- cuit is converted to a cyclic graph with the gates as the nodes and the signal wires as the edges, the connections between x and y form a cycle with two paths, as shown in Fig. 3.2. Hence, the detection of signals that might exhibit spatial correlation resolves to identify possible cycles in the circuit. For example, in Fig. 3.2, a cycle would be detected that goes through A a A b A. In the study by Hassan et al [90], a depth-first search algo- rithm is used to identify such loops in the design. The algorithm starts with the circuit primary inputs i, and