pen plotters?

Tony Duell wrote: You are correct, I noticed after sending the message that my phrasing was ambiguous or misleading. The plotter has two ports, one for HP-IB and one specifically for a connection For some reason the package I received came with both the 98130 interface (9815->9872) as well as the 98135 interface (9815->HP-IB). Given the HPI-IB interface already on the plotter, this would seem to be redundant, as I don't think this 9815 was used with any other HP-IB devices. Going by the doc though, it appears that the firmware in the 98130 may make for much easier programming of the 9815 to control the plotter, compared to going through the generic HP-IB interface. I don't have the schematic and haven't RE'd it, but am aware of the 6800. Having written some assembler code for the 6800 and being somewhat aware of object sizes for such, I think when I looked inside the 9815 I was somewhat surprised that they managed to fit all the firmware code into (IIRC) 2KB of ROM, considering all the math functions, programming capability, tape-drive control, printer control, etc. that would be in there. Either that or I missed seeing a ROM chip somewhere. Another list member provided some references http://en.wikipedia.org/wiki/HP_2100 http://www.hp9825.com/html/hybrid_microprocessor.html which provide some more explanation of the lineage and some details of the chnages from the 2100 arch. Even Adam Osborne's 1976 book "An Introduction to Microcomputers - Vol II - Some Real Products" - which gives a pretty good overview of the microprocs available at the time - makes no mention of it.