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What is the difference between HFN and CTS?

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mujju433

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what is the difference between HFN and CTS?
 

cooldude040

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HFN and CTS

HFN means i think High fanout net
 

sree205

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HFN and CTS

CTS is clock tree synthesis. Clock is an example high fanout net(HFN). We declare any signal such as reset or enable, which will be supplied to a lot of flops, as high fanout net during synthesis. Incase of clock, i think the tool understands that clock is a HFN and assumes its going to be updated in later part of the process with buffers of higher drive strength and treats it as an ideal net. So, my guess is, it need not be specified as a HFN.
 

shelby

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HFN and CTS

reset signals are an example of HFNs since they go all over the place. During CTS you add buffer trees to you clocks and all other HFNs
 

csmode

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HFN and CTS

yes ,generally set and reset pins are HFN out nets, to minimize insertion delay and fanout we build buffer tree during CTS.but these r not constrained much like clk in clk spec
 

ac123

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Re: HFN and CTS

scan enable is another example for High fanout net. Some of the P&R tools are intelligent enough to detect the high fanout nets during placement optimisation (based on the threshold given for no: of nets) and do HFN synthesis.
 

iwpia50s

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HFN and CTS

Most tools today understand the difference between HFN and clocks. Typically you can set the threshold of what is defined as an HFN, but the tool default is fine. HFN synthesis typically tries to me requirements like max cap, max slew, max fanout.
 

rajesh9999

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Re: HFN and CTS

You can create clock tree like structure (with buffers and inverters) for HFN to satisfy design rules (max cap, slew etc). The command in PKS used to be - build physical tree <net_name>.
 

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