I'd like to know about the TLCS-870 and TLCS-870/C1 instruction sets and
opcodes.

However, I only find incomplete information.

For the TLCS-870, there is something at www.datasheetarchive.com, but it
is only 20 pages and looks like there should be more (details are only
available on data transfer and exchange instructions; arithemtic, jump,
etc are missing).

For the TLCS-870/C1, there is a pdf titled "TLCS-870/C1 Series
Instruction Set" at toshiba.semicon-storage.com, but it is only 71 pages
and looks like there should be more (details are available on most
instructions, but e.g. call and return instructions are missing).

Any ideas about where I could find complete documentation?

Philipp