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Method of improving a placement in layout design

  • US 4,975,854 A
  • Filed: 05/22/1987
  • Issued: 12/04/1990
  • Est. Priority Date: 05/23/1986
  • Status: Expired due to Fees
First Claim
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1. A layout placement method for a wiring grid with a plurality of cell rows, separated by wiring regions, each cell row having a plurality of cells, the method comprising the steps of:

  • (a) for each cell row inputting to a logic connection information file a number and type of variable size blocks, each block containing an integral number of cells and reading from a preprogrammed library a required number of cells for each block type input for a row,(b) inputting to the logic connection information file a number of block terminals for each block,(c) counting a number of empty cells of each cell row,(d) calculating a number of required empty cells for each row from the number of blocks, the number of block terminals and the number of empty cells, by;

    (i) determining an average cell row terminal density equal to the total number of terminals in the cell row divided by the total number of cells in the cell row, and(ii) determining the number of required empty cells for a block by finding the difference between the number of block terminals in the cell row divided by the average terminal density of the cell row and the number of cells in the block,(e) calculating for each row one of an excess and deficiency of the required empty cells from the difference between the number of empty cells and the number of required empty cells,(f) distributing blocks on the wiring grid to compensate for the calculated one of the excess and deficiency, and(g) locating the distributed blocks on a base structure of the wiring grid.

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