plotters again

[Tony Duell]

> 
> Tony Duell wrote:
[HP9815 interface conenctor on the HP9872 plotter, and the fact that it's 
bidirectional]

> > 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.
> 
> Not that I have seen.

OK, do you know this for certain, for example by doing tests on the 
system, disassembling the ROM in the 98130 interface or whjatever, or are 
you guessing it like I did? 

> 
> 
> Tony Duell wrote: 
> > 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.
> 
> Brent wrote: plotter HP-IB port that does just the data transfer
> (minus all the HP-IB device selection, etc. functions)

You claimed it was an HPIB port! It isn't.

> 
> Brent wrote: the 8 HPIB data lines and 3 data-handshake lines are brought across
> to the controlling machine. It's HPIB minus everything but the data-transfer.

Ah, but it's not/ There's a trivial corrrection that i's only 7 data 
lines, and a more major one that it's darn well not HPIB. If it was 
truely HPIN, then without the ability to receive commands, it can't be 
bidirectional. Read the IIEEE-488 standard if you don't believe me (I 
have read it).

> 
> Brent wrote: plotter microproc is distinguishing 9815 vs HPIB and acting appropriately.
> 
> Brent wrote: un-addressed talk/listen HPIB-style data transfer.
> 
> I never suggested it was HPIB in any sort of strict or complete sense. I said
> it did not include the device addressing, which precludes direction selection
> via device addressing. I never even raised the issue of direction selection,
> you did, but as a declaration not a question. All I said was HPIB data
> *transfer*. 

OK, it uses the HPIB 3-wire handshake. I think that much is clear from 
the schematics. I was (and still am) interested in knowing how it 
revereses the transfer direction. I've _guessed_ it was done based on the 
2 devices (9815 and plotter) knowing what commands would cause the 
plotter to send back data and knowing how to determine the end of that 
data. But is that known _for sure_?


 
> 
> Tony Duell wrote:
> >I know what you've said, but _I_ have a problem with it.
> >What you're describing is, I beleive, technically impossible.
> 
> Apparently if one comes to a conclusion before you, it's technically impossible.

Not at all...
Noe I said 'I believe'. Not 'it is'. In other words, I am not sure. I 
still believe (and will continut to beleive until somebody shows me how 
it can be done) that a trune HPIB system without addressing fuctionality 
can't be bidirectional. A device that changes from being a listener to 
being a talker without receiving addressing commands is not an HPIB 
device. 

> I originally asked for HPGL plotter files. You just had to weigh in with your
> (unsolicited) expert opinion about the interface. I kept indicating it didn't
> seem like a big issue of complexity or concern.

Hang on a second. Last time I checked this was a list for discussing 
classic computers and their peripherals. It is not a list to provide you 
(or anyone else) with your wants (in this case HPGL files). If you post 
about a machin, its quite possible you'll get a thread started that goes 
off in direction you'd never anticipated. If you don't like that, well, 
tough!

I make no secret of the fact that I like HP desktop calculators. I am 
interested in them and their peripherals. And I openly admit to not 
knowing everything about them. I also said from the start that I'd neve 
seen a 9872 plotter or its interface. The reason I started asking about 
it was to _learn something_. This might be an alien concept for you, but 
some of us don't know everything.

> If you were confused or wondering how I thought it worked you should have
> asked a question. Instead you kept making declarative statements, many of which

Oh come on... I did ask questions. You could also have tried correcting 
my comments _with verifyable facts_ -- that is, stuff from the manuals, 
stuff from your own measurements. Or even just guesses ('Well, it can't 
be true HPIB, but the way it changes direction could well be...'). 
Instead you flame me. 


> strayed well away from anything I had expressed any concern over. It was all about
> Tony's expert opinion and advice.
> 
> Get over yourself.
> 

Pot. Kettle. Black.

-toyn