I’d somehow missed this, the 8051 being perhaps the 3rd CPU I got a little familiarity with - Intel (and second sources) offered the 8052 microcontroller with a built-in Basic. Apparently useful for fire alarms, burglar alarms and other kinds of not-realtime industrial control.
Here’s a project, by Madis Kaal, which uses it:
My 8052 BASIC Project
Some time in early 80-ies Intel produced a mask-programmed 8052 MCU which contained a floating-point Basic interpreter with lots of interesting features, including built-in support for EPROM storage of BASIC programs.
*MCS-51(tm) BASIC V1.1* READY >
Many further links on the project page, including a link to this second, improved, project:
Fully configured 8052-BASIC core
After building my first 8052-BASIC project I learned that there is more to that Basic that shows up on a surface. The most important fact is that it looks for extension ROMin code memory space and if couple of bytes check out during boot, tries to call initialization code and does other interesting things in that ROM space. So the method to map 32K of RAM to both code and data space is not a very good idea at all, possibly resulting a crash at startup…
See also the helpfully HTML-ified manual:
BASIC-52 Reference Manual