Connection checks

laylight keeps track of how ports are connected:

placing one port on another is a declared connection;
two ports that end up at the same position, pointing the same way or opposite ways, are connected geometrically. That includes a cell's own marker lying on a port of one of its instances — which is how an exported port is recognised.

laylight check then looks for mistakes, and on this page Submit does the same:

a port of an instance that is connected to nothing is dangling. It is only a warning, but usually a sign of a forgotten component or of a port that should have been exported;
connected ports of a different type or width are an error.

The laylight netlist and laylight lvs commands go one step further: they write the connections out as a netlist and compare them with a reference netlist.

Exercise

Link joins two waveguides, but Submit finds three problems. Make the second waveguide as wide as the first, then export the two free ends as the ports input and output of Link (type "waveguide", the matching direction, width 500 nm).

import "tech.lyl" cell Waveguide { param { length size = 10um width size = 500nm } marker { input { at core.left_center with type = "waveguide", direction = "input", width = width } output { at core.right_center with type = "waveguide", direction = "output", width = width } } layer si { shape rect with length, width as core place core.left_center at self.origin } } cell Link { place { Waveguide at self.origin as a Waveguide with width = 800nm at a.marker.output[0] as b } }