Add Peripheral Filler Cells (with 1.0 μm snap grid)

A number of students experienced problems with the example pad ring during the place and route lab on Thursday.

Having looked into the problem in more detail it seems that the best solution is not to use the smallest of the I/O filler cells (with a width of 0.1 micron). This can be arranged if the distances between adjacent pads is divisible by 1.0 micron.

I have written some TCL code which you can include in your scripts between the “amsUserGrid” instruction and the “amsFillperi" instruction which should move the pad cells into suitable locations:

# Snap the pad cells to the 0.1 um grid
   amsUserGrid


# Now ensure the spaces between cells are multiples of 1.0 umicron
   set pad_height 340.4
   set scale [dbGet head.dbUnits]
   set snap_grid [ expr int( 1.0 * $scale ) ]
   foreach pad [concat [dbGet -p2 top.insts.cell.baseClass pad] [dbGet -p2 top.insts.cell.baseClass corner] ] {
     set name [dbGet $pad.Name]
     set master [dbGet $pad.cell.Name]
     set orient [dbGet $pad.orient]
     set x [dbGet $pad.pt_x]
     set y [dbGet $pad.pt_y]
     if { $x != 0 } {
       set xint [ expr int( ($x - $pad_height) * $scale ) ]
       set xrem [ expr $xint % $snap_grid ]
       if { $xrem != 0 } {
         puts "Found off-grid instance (x): $name $master $x $y $orient"
         set newx [ expr ( double(( $xint / $snap_grid ) * $snap_grid) / $scale ) + $pad_height ]
         dbSet $pad.pt_x $newx
         puts "  x position corrected $x -> $newx"
         set x $newx
       }
     }
     if { $y != 0 } {
       set yint [ expr int( ($y - $pad_height) * $scale ) ]
       set yrem [ expr $yint % $snap_grid ]
       if { $yrem != 0 } {
         puts "Found off-grid instance (y): $name $master $x $y $orient"
         set newy [ expr ( double(( $yint / $snap_grid ) * $snap_grid) / $scale ) + $pad_height ]
         dbSet $pad.pt_y $newy
         puts "  y position corrected $y -> $newy"
         set y $newy
       }
     }
   }

# Add peripheral filler cells

   amsFillperi