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how to identify that those nets should be in same length

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selvakumar.m

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how to identify that those nets should be in same length?. i dont know how to analyse the length matching information in datasheet.where the length matching information will be given in the datasheet for particlar ic?.
for eg: AT91SAM9261B-CU-ND
 

marce

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Depends on what the interfaces connected are going to be. If you have a DDR memory interface, there will be an application note, or info in the memory chip data sheets. Same if a phy is attached.
When contraining the signals, you have to consider the complete circuit diagram, not just one IC.
 

praveenlb

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If you are seeing in allegro tool go to constraint manager their select routing and click on total etch length ..there you can find each net length..select it .it will be highlated.
Regards
Praveen Bhat
 

ea.arun

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length matching is done to achieve adequate set up/hold time requirements in case of a digital chipsets which can be violated due to the line propagation delay between the signals referred to a reciever.....for example in DDR, the datasheet set up/hold time datas can be used as reference(for ex: b/n data and DQS line) for the timing deration.......you can find alot of application notes around about length matching concepts.....
 

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