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Logic Synthesis & Physical synthesis ?

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manivannanrm

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post logic synthesis

Can anybody explain Logic synthesis and physical synthesis ?
And its difference ?
 

Logic synthesis just translate RTL to netlist , and some physcial information is not accurate (such as wire load model, cell place).
phsysical synthesis can get some physcial information from layout, it physcial information is accurate than logic synthesis. And some physcial synthesis not only translate RTL to netlist , it can translate RTL to Layout.
And usally some logic synthesis tools have the command to read some physical information. such as "read_spef" in dc to read floorplan . But how to use it , i don't clearly.
 

logic synthesis just do translating and mapping .
but physical synthesis do floor planning . and trial layout . It will
help physical designer to determine the blocks relationship . and give a good timing result .
 

tnz for ur answers.

Can I say physcial synthesis as complete backend (starts from floorplanning to routing).
The logic synthezed file format will be .v ,what abt phys.synt. file format?
 

manivannanrm said:
tnz for ur answers.

Can I say physcial synthesis as complete backend (starts from floorplanning to routing).
The logic synthezed file format will be .v ,what abt phys.synt. file format?
No, physcial synthesis is start from your RTL code
 

"Can I say physcial synthesis as complete backend (starts from floorplanning to routing).
The logic synthezed file format will be .v ,what abt phys.synt. file format? "

The equivalent file for physical synthesis is DEF. DEF is an industry format that encapsulates physical information. At any given stage if you write out .v and .def you will have saved the database and can start from the same point again by reading the .v and .def.
 

normal synthesis has wire load models where are in Physocal synthesis wireloads are excluded and physical information ( like floor plan location etc ) are fed in . In addition to normal db file libraries with physocal information ( pdb or milkway ) is read in the tool for optomizatiomn. The end result is give rialisitic view of timing
 

The answers were helpfull.
But still I have one doubt where does the term phy. synthesis will be used I feel that from fplanning to routing.Please correct me if i am wrong.
Previously there is an answer as it starts from rtl code.

tnx in advance
 

hi manivannanrm

As answered above physical synthesis will start from rtl , the other option is you can take the logical synthesized netlist as a input and you can synthesis with power models (for all cells) in place of wlm (wire load model)
 

physical syn will do the virtual floorplan first, and then i can calculate the wire delay vaule which is near to the real floorplan, so the resule it's very

Added after 1 minutes:

physical syn will do the virtual floorplan first, and then i can calculate the wire delay vaule which is near to the real floorplan, so the resule it's very
 

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