plotters again

[Tony Duell]

> 
> Tony Duell wrote:
> 
> > My guess, and it's only a guess, is that it works something like this :
> > At power-up, if the 9815-mode line is asseeted, the plotter goes into
>                                                               ^^^^^^^^^
> > listen mode (the HPIB talk/listen modes can be controlled from the
>   ^^^^^^^^^^^      ^^^^
> > plotter's microcontroller, this is also used for self-tests on the HPIB
> > interface, as it is on the 7245...). The 9815 talks and sends it data.
>                                                 ^^^^^     ^^^^^    ^^^^
> > If the poltter gets a command that should output data (say a digitise
> > command), it goes into talk mode automatically and sends said data. The
>                          ^^^^ ^^^^ ^^^^^^^^^^^^^     ^^^^^      ^^^^
> > 9815 side of things knows it's just sent such a command and goes into
> > listen mode to recieve said data.
>   ^^^^^^^^^^^    ^^^^^^^      ^^^^
> 
> Good for you, you've finally got it.

Is this docuemtned anywhere? I can't see it in the 9872 operating/service 
manual, but as I said I've not seen the 98130 (9815 plotter interface) 
manual. 

> As I said previously: un-addressed talk/listen HPIB-style data transfer.

HPIB-style, but not HPIB!. It may use the HPIB lavels, it may use the 
same 3 wire handshake, but it's not HPIB if it changes direction like 
that without any commands fromt he controller. That's what confused me. 
You kept on insisting it was HPIB, I still claim that, strictly, it can't be.

-tony