Machine

The handful of settings that belong to the whole machine rather than to any one device, and are therefore not part of a configuration.

Bus

Platform is QBUS or UNIBUS, fixed when the software was built. It is what the card is, not a choice.

Address width is the CPU’s — 16, 18 or 22 bits on QBUS, 18 on UNIBUS. Changing it re-bases the I/O page, so it applies only while the bus is halted. Asked for on a running machine the setting is left alone and the interface says why.

External console

Where the real machine’s console line is read from. Which you want follows from the processor in the box, and getting it wrong is the most common reason a console appears dead.

Source
BBB /dev/ttyS2	a UART on the BeagleBone backs the console. This is for a processor with a serial line of its own — an 11/53, an 11/73 — whose console connector is cabled to the cape.
Web Serial	a USB serial port on the machine running the browser backs it instead. A Connect button appears; Web Serial needs a one-time grant to reach the port.
Off	nothing does — and the port is then free for QUniLator’s own emulated DL11 to be the console. This is for a processor with no console of its own, and for an emulated processor, which has its own.

Baud must match what the processor’s own line is jumpered for.

Garbage means the baud is wrong; silence means the cable is

A mismatched speed still delivers characters — ôôôôWWô and the like. A line that produces nothing at all, in any CPU state, is not connected.

Rather than waiting for the machine to speak first, assert HALT and press Return: a halted processor sits in micro-ODT and answers. That works at any moment, with no boot and no guest.

One thing at a time on that port

With the source set to ttyS2, the bridge holds the port. Enabling an emulated DL11 that also names ttyS2 does not take it — the device quietly stays off, and only the log says so. On a processor that has its own console, leave DL11 disabled: a second SLU at 777560 would be two cards answering one address.