Hi everybody,

I have a calculator HP9810A and a plotter HP9862A, both connected by the corrsponding interface cable. The calculator I had repaired some time ago. Now I'm trying to get the plotter to work.

As far as I know the plotter can be controled by the calculator by the key sequences <FMT> <arrow up> and <FMT> <arrow down> which will move the pen to the position given by the x and y registers with pen down or pen up respectivily.

Unfortunately it does't work. If I'm doing one of the key sequences the display gets dark and I have to switch the calcuator off and on before I can do a next try. If the plotter interface is removed from the calculator, the key sequences don't do anything and the calculator is not blocked by them.

With an oscilloscope I have seen, that the plotter gets a signal (the control line gets activated very shortly) and gives a response to it (the flag line gets active for 4ms).

Before diving deeper into the circuits, I have a question: Is a ROM required to use the plotter? There is a ROM in the calculator labeled "PLOTTER PRINTER ALPHA 11261A". As far as I have seen the plotter gets its signals from the calculator without this ROM too. Is this ROM reuired or are the necessary routines in the ROM of the calculator already?

I have the service manual to the plotter with the schematics of it. In it no word on this ROM can be found. Unfortunately I don't have any documentation on the ROM itself. As far as I have seen, it supplies the alpha numerical printing functions for the printer build into the calculator and this work. But I don't know what and how it can do for the plotter.

Can somebody give some hints on the functionality of this ROM?

Best regards and thanks,

Thomas Falk

Edited: 7 Dec 2013, 9:50 p.m.