Datasheet, then check with the scope/logic analyzer whether the various bus control signals are there. That's how I would start checking that. It is the old 8048 Intel MCU family which is well known, so the documentation shouldn't be hard to find.
That MCU has no internal memory by itself, so if it is not attempting to access the external one, it is likely dead. But check also whether it is getting reset properly, whether there is clock, etc. The usual stuff.