CASIO PB110's memory OR-4?

[Jeff_Birt]

The PB-110 can use a PR-1 according to the manual. Link below.

I have spent a lot of time investigating how the OR-1 works and even had a PIC processor working as an OR-1 on a PB-100. Doing this I found there are two different ROM versions in the PB-100 the later version is capable of addressing 2K of additional RAM but no such modules were made. Eventually I'll get back to this project as I'm hoping to be able to make new OR-1 (OR-2?) modules.

https://archive.org/details/manual_PB110_OM_CASIO_EN