Patent ID: 6327694
Filing Date: 2001-12-04
Classification: G06F

Abstract:
A cell placement apparatus for use in computer aided design automation, comprising:a restricted region specifying module specifying both a restricted region in which is restricted a cell activity ratio indicative of a ratio of a cell occupied area to a chip surface area and a cell maximum activity ratio of said restricted region;a restricted region managing module accepting for management said restricted region and said cell maximum activity ratio specified by said restricted region specifying module; anda cell placing module placing cells in such a manner that said cell activity ratio of said restricted region managed by said restricted region managing module does not exceed said cell maximum activity ratio, whereinlet s1 and s2 be cell areas in a first region and a second region, respectively, which are obtained as a result of bisecting, s (=s1+s2) be a total cell area, S1 and S2 be areas of said first region and said second region, respectively, S1(i) be an area of a portion belonging to said first region within an i-th restricted region, S2(i) be an area of a portion belonging to said second region within said i-th restricted region, and .rho.(i) be a cell activity ratio specified for said i-th restricted region, thensaid cell placement control module figures out areas S1(0) and S2(0) of portions having no cell activity ratio restriction in said first region and said second region, respectively, fromS1(0)=S1-.SIGMA.S1(i)S2(0)=S2-.SIGMA.S2(i)and whereinsaid cell placement control module then figures out an activity ratio .rho.(0) of a portion having no cell activity ratio restriction, from.rho.(0)={(total cell area)-(total cell area of activity ratio specified regions))/(total area)=[s-.SIGMA.{.rho.(i).times.(S1(i)+S2(i)}]/S1(0)+S2(0)and whereinsaid cell placement control module then figures out cell effective areas s1' and s2' in said first and second regions, respectively, based on said activity ratios .rho.(0) and .rho.(i), froms1'=.rho.(0).times.S1(0)+.SIGMA.(.rho.(i).times.S1(i))s2'=.rho.(0).times.S2(0)+.SIGMA.(.rho.(i).times.S1(i))and whereinsaid cell placement control module then figures out converted areas S1' and S2' by proportionally dividing a total area of said first and second regions by ratios, to a total cell area s, of cell effective areas s1' and s2' in said first and second regions, respectively, usingS1'=(S1+S2).times.(s1'/s)S2'=(S1+S2).times.(s2'/s)and whereinsaid cell placement control module then provides a control of grouping of cells effected by said partitioning based placing module so that an absolute value of a difference between ratios of cell areas s1 and s2 to said converted areas S1' and S2', respectively, of said first and second regions, respectively, satisfies a condition.vertline.s1/S1'-s2/S2'.vertline..ltoreq..alpha..