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Should memory macros provide a SITE definition?

acowan

We're having a debate amongst a few engineers as to which is better:

LEF for a memory macro should not have a SITE,

or...

LEF for memory macro should define a unique SITE

Please help us. We'd like to know the PRO's and CON's of each.

Case 1 example: no site

MACRO sramH20_wrapper
 FIXEDMASK ;
 CLASS BLOCK ;
 ORIGIN 0.0000 0.0000 ;
 SIZE 63.8400 BY 35.5200 ;
 SYMMETRY X Y ;
 PIN VSS
  DIRECTION INPUT ;
  USE GROUND ;
  PORT
    LAYER VIA5 ;

....

Case 2 example: define a site with the macro

SITE SITE_sramYT
 CLASS CORE ;
 SIZE 380.010 BY 495.760 ;
 SYMMETRY X Y R90 ;
END SITE_sramYT

MACRO sramYT
 CLASS BLOCK ;
 FOREIGN sramYT 0.000 0.000 ;
 ORIGIN 0.000 0.000 ;
 SIZE 380.010 BY 495.760 ;
 SYMMETRY X Y ;
 SITE SITE_sramYT;
 PIN VDD
  USE POWER ;
  DIRECTION INPUT ;
  PORT
     LAYER metal5 ;

Which is better?

  • In my opinion, creating sites and rows for macros is a lot of unnecessary work. They are not required, and in the initial floorplanning stages, you are likely to move macros around quite a bit. Why have to re-create rows every time? Just move the macro and be done.

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