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http://mantravlsi.blogspot.tw/2014/08/wire-load-model-wlm_1.html From the link, there is an instance of snapshot of a WLM.I can not figure out the number "1" in fanout_length("1",0.002) of the instance.Is it meaning length unit?Or output number of fanout?Why is it different with different with length of wire?

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closed as unclear what you're asking by Andy aka, Voltage Spike, Sparky256, Finbarr, uint128_t Feb 25 '18 at 15:02

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No. "1" means Fan-out and "0.002" means the corresponding wire length in the units mentioned in the cell library. Fan-out means no. of outputs driven by a gate. For eg. Suppose in the synthesized design, two outputs are being driven by an AND gate. It means the Fan-out of that gate is 2. Therefore for that gate, the algorithm will take the value for (2, 0.006) from the wire load model library, for estimating the wire length and hence delay at pre-routing stage. It uses the value "0.006" to calculate the R and C components distributed in the wire.

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  • \$\begingroup\$ thank you . it is very helpful!!One more question , is the number the output gate or input gate? \$\endgroup\$ – user3857054 Feb 20 '18 at 23:12
  • \$\begingroup\$ Fan-out is related with Output of a gate. Fan-in concerns about input of a gate. \$\endgroup\$ – Mitu Raj Feb 21 '18 at 11:53

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