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About GCELLGRID and TRACK Statement in DEF

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How are the parameters for following statements used in DEF file calculated GCELLGRID TRACK For example, in a DEF file, statements appear as: TRACKS Y 500 DO 146 STEP 1000 LAYER metal1 ; GCELLGRID Y -50 DO 2 STEP 9950 ; GCELLGRID X 173250 DO 1 STEP 7450 ; How are the parameters for these statements calculated. GCELLGRID and TRACK are two of the statements which are used to define the floorplan for a particular design. But, how are the values for these statements calculated? Thanks.


Originally posted in cdnusers.org by johariph
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  • Yes your are right, I checked DEF reference, and the half-track offset is the default. But, I got this question since, FE is using 1600 offset by default for metal6. The metal6 pitch in LEF is 1200 (Real 1.2u). And there is no Offset definition defined in my LEF file for metal6. So logically, FE should have taken 600 as an offset by default for metal6, then why 1600? No, I am not using DEF TRACKS and GCELLGRID from somewhere else, FE is creating it for me. Moment I load the netlist and libraries (conf), it creates the floorplan. But the offset used for metal6 is troubling me. Infact, I tried various designs with same libraries, and it always uses same offset and pitch combination. So, if FE expects to get these values from LEF, and does not found, it should have taken default values. Well, FE displays following message about offset for metal1 and metal2 Horizontal Layer M1 offset = 500 (guessed) Vertical Layer M2 offset = 400 (derived) Suggestion: specify LAYER OFFSET in LEF file How does it guess for other layers (metal6 for ex:) ----------------- I feel, GCELLGRID affects the placement and routing both, but I don't know exactly how. The reason I need this information because, I have to modify my placement little bit manually. So if core area increases in this process, there would be change in floorplanning also. I want to know this information so that I can decide, if there is a big impact on floorplan or if I can keep it as original (since core area may increase only marginally)


    Originally posted in cdnusers.org by johariph
Reply

  • Yes your are right, I checked DEF reference, and the half-track offset is the default. But, I got this question since, FE is using 1600 offset by default for metal6. The metal6 pitch in LEF is 1200 (Real 1.2u). And there is no Offset definition defined in my LEF file for metal6. So logically, FE should have taken 600 as an offset by default for metal6, then why 1600? No, I am not using DEF TRACKS and GCELLGRID from somewhere else, FE is creating it for me. Moment I load the netlist and libraries (conf), it creates the floorplan. But the offset used for metal6 is troubling me. Infact, I tried various designs with same libraries, and it always uses same offset and pitch combination. So, if FE expects to get these values from LEF, and does not found, it should have taken default values. Well, FE displays following message about offset for metal1 and metal2 Horizontal Layer M1 offset = 500 (guessed) Vertical Layer M2 offset = 400 (derived) Suggestion: specify LAYER OFFSET in LEF file How does it guess for other layers (metal6 for ex:) ----------------- I feel, GCELLGRID affects the placement and routing both, but I don't know exactly how. The reason I need this information because, I have to modify my placement little bit manually. So if core area increases in this process, there would be change in floorplanning also. I want to know this information so that I can decide, if there is a big impact on floorplan or if I can keep it as original (since core area may increase only marginally)


    Originally posted in cdnusers.org by johariph
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