I could have sworn that at one time PPC or CHHU published a spec or at least a technical description of the 1LG9 ROM, but I can't seem to find it now. Does anyone else know where it was found? Or am I just hallucinating?
The 1LG9 120Kbit ROM (3 pages of 4Kx10) was used for the 41CX mainframe ROMs, the 41C and 41CV halfnut mainframe ROM, the 82242A "Blinky" IR printer module, the Advantage ROM, and any other 12K application ROM modules. It was HP's first (and probably only) chip to support ROM bank-switching on the 41.
The 1LG9 could be configured to be hard-addressed or port-addressed, with selectable bank switching (not used for the base mainframe ROM).