On over-the-cell channel routing

Priority driven channel pin assignment

“…It has been extensively studied in the past ( [15], [5], [19], [7], [lo], [12]). Advanced (over-the-cell) channel routers consider the terminals (pins) on the two sides of the channel not completely fixed a t the beginning of the routing phase ( [17], [a], [6], [ll], [13], [IS]). This approach enables further channel density reduction.…”

“…We prefer type 3 decisions having the same net on the top and on the bottom of the current column. Columns with different nets on the top and on the bottom cause edges in the vertical constraint graph :(16) if net(ti) = net(bj)(17) then Iiacrease P3 else Decrease P3 *Note that d l ( p , q , L ) is the channel density and dz ( p , q, L ) is the decision type for the last coluinn: d * ( p , q , L ) = 3 means that both t, and h, have to be placed to position L. dz ( p , q , L ) = 2 (= 1) ineans that just b, (t,) has to be placed to position L. And d z ( p , g , L ) = 0 means that neither t p nor b, are assigned to L.…”

A new approach to over-the-cell channel routing

“…Recently, a new type of cell models where all the pins are inside the cell has been introduced. Algorithms for this type of cell models can be found in [9,14,[19][20][21][22].…”

“…The authors in [20] considered the problem for the case where only one metal layer is available for routing in each of RT and RB , and gave a heuristic algorithm without details. Later, the authors in [21] presented an optimal algorithm that generates a planar routing in each of RT and RB while minimizing the resulting channel density. The authors in [20] also considered another case where two metal layers are available for routing in each of RT and RB but without the presence of vias between the two layers, and presented a heuristic method.…”