A study is made of the channel pin assignment problem subject to both position and order constraints. The authors show that the problem is NP-hard in general and present a polynomial time optimal algorithm for an important case where the relative orderings of the terminals are completely fixed. They extend their algorithm to solve the problem for the case where there are also separation constraints between some pairs of consecutive terminals optimally in polynomial time. A discussion is presented of how the algorithm can be incorporated into standard cell and building-block layout design systems. Experimental results indicate that by allowing movable terminals, substantial reductions in channel density can be obtained.