If you were to look around for what's in a terminal, you'd see that the '2051 is an extremely poor choice for use in a terminal. The '89S52, though it's an ATMEL product, which I personally would avoid, is probably a much better choice, since it allows you to use external RAM. What you'd do is to write to your external RAM, and then use external logic, perhaps in the form of programmable logic, to perform the timing, character generation, etc, even with the aid of a character generator ROM/PROM and then drive a video modulator so that it could be fed to a standard TV set.

All of those things were done with discrete logic back in the '70's and thereafter, so you should have no trouble finding examples in, say, the APPLE-][ schematics, etc. "Special" chips for your purposes are probably no longer available, as what you want is a cheap subset of what's likely to be available today. The '89S52 probably isn't fast enough to do what Phil Gallo did with the DS89C420 so, while study of that project can help you understand what's required, you probably will have to look elsewhere.

Once upon a time there was an MC6847, which might suit your purposes, and it was intended to drive a standard TV set. That might be worth a look though I doubt you can buy it today.

RE