All the above is true but.. The 8049 if masked has a pin (just like the '51 that allow external memory chips. The chip programs like an old 2708 as that is the era of the technology. Most programmers will program the part. there are plenty of shareware assemblers for the chip and the good one handle off page jumps (at least with warnings).

a '51 would be prefered but the chip and i did have some fun back in '79 thru '85