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DC question about "set_dont_touch" command

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sree205

sree205

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Hi all,
i've a question regarding one of the design compiler commands. "set_dont_touch".

its used to make sure that some of the cells in the library are not used for synthesis. can anybody suggest why some cells should not be considered ? i can think of one options, but, am not sure of other options.

1. large fanout cells, probably not necessary for low gate count design.

if anybody has any other ideas, please share.
 

DC question

You are misunderstand "set_dont_touch" with "set_dont_use".
"set_dont_touch" is some hard mirco or clock you don't want synthesis tool to change it.
"set_dont_use" is not to use certain cells.
 

Re: DC question

love2read said:
You are misunderstand "set_dont_touch" with "set_dont_use".
"set_dont_touch" is some hard mirco or clock you don't want synthesis tool to change it.
"set_dont_use" is not to use certain cells.
Click to expand...

avoid LATCH, for sync design.
 

DC question

love2read, yes, u r right. it should've been set_dont_use.
 

Re: DC question

i think not all cells in target library can be use for synthesis, especially for synchronous synthesis, for example, latch should be set_not_use.
a designer should have a clear understanding on cells' usage in lib to obtain a excellent implementation.
 

DC question

set_dont_use : avoid buf for clock trees in circuit.
 

DC question

hi all,

we use the set_dont_use command to avoid those cells which we dont want to use in the synthesis.
1.the high strength cells(X16,XL etc).bcz they will consume high power and some more porblem with those cells in the p&r.
2.the clock buffer/inv.bcz they will be used while building the clock tree.
3.some tristate cells and latches .they will be used according to the requirement.
4.jkflops,sr-flops.they will be used according to the requrement.

regards,
rameshs
 
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