pen plotters?

Brent Hilpert hilpert at
Wed Feb 14 19:17:37 CST 2007

Tony Duell wrote:
> >
> > Tony Duell wrote:
> > > The thing I am looking for (in the UK for obvious reasons) is an HP9862
> > > plotter with 9800-series interface module. Little chance of getting one,
> > > though.
> >
> > I have an HP9872A with both the 98135A interface module for HP-IB and the
> I'm probably mis-remembering the numbers, but isn't the 98135 the HPIB
> interface for the 9815 calculator? I thought hte plotter had HPIB as
> standard.
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
from the 98130A interface in the 9815.

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

> I don;t know how much you know about the 9815 internals, but anyway. It's
> a 6800-based design -- apart from the firmware ROMs, all the chips are

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.

> > What I find interesting is the plotter has a 16-bit 5MHz single-chip
> > microprocessor (identified in the service manual only as "HP Microprocessor
> > (P.N. 1818-2500)") - pretty spiffy for 1977. One of HP's internal developments
> I've come across that processor in the HP7245 thermal printer/plotter.

> > that I don't hear or see much info about. The service manual doesn't provide
> > any info about the microproc internal architecture.
> I've not found out anyhting about it, 

Another list member provided some references 

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.

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