profile/termination

Remedy ¶

Fit the termination the bus calls for across the pair, at the physical end of the bus rather than partway along it.

What it means ¶

A profile’s bus needs termination, as a differential pair like CAN’s CANH/CANL or RS-485 does. The profile is in use, but nothing bridges its two designated signal nets through series passives, so the terminating resistor is missing.

Why engineers want it ¶

A differential bus with no termination reflects its own signal off the unterminated end. At low speed the link often works, so the omission survives bring-up; under load or at rate the reflections corrupt data and the fault reads as intermittent, hard-to-localize bus errors rather than an obvious dead link. Termination is easy to forget precisely because its absence is not immediately fatal.

How it is checked ¶

terminated(?h) is derived when a high-suffix net (e.g. _CANH) net.reaches a low-suffix net (_CANL) through the series-passive walk. That walk crosses only 2-net R/L/ferrite/fuse elements, so it finds the terminating resistor across the pair but does NOT cross the multi-pin transceiver that legitimately drives both lines. The walk is transitive, so it also accepts a split termination (two 60Ω resistors with a midpoint). When the interface is in use (the confidence gate holds) and nothing terminates the pair, the high net is reported as unterminated. The terminated fact is board-wide, so a board with two buses and one terminator reports both as terminated. The two suffixes are the requirement’s high/low params, so the same compiler serves any differential bus that names its pair by convention.

For software readers ¶

It is the topology assertion “somewhere in the graph, one node must connect these two specific edges.” The signals can each be present and fully wired (presence and dangling checks pass) while the bridging element between them is absent, like two services that are both up and reachable but with no configured link between them.