Benson 1645 plotter experience?

From: Tony Duell <ard_at_p850ug1.demon.co.uk>
Date: Sun Jun 13 12:21:00 2004

>
>
> Anyone ever used a Benson 1645-R plotter?

No, but something you said jogged a memory of a feature of an HP plotter.

>
> We also have an 'SW' interface module, which has two ports on it - one
> male and one female. According to the (nearly useless) documentation we
> have, one is for a terminal and one for a host computer - but it doesn't

THis is the bit that jogged my memoey. Some HP RS232 interfaced plotters
(And, IIRC, at least one Tektronix one) could be connected between a
terminal and a modem. Normally the plotter ignored the data on the serial
line, and just 'connected' the terminal to the modem (and thence to the
host), but if it received the right control code, it started
interpretting data from the host (and didn't pass it to the terminal).
The idea was so that you could have a 'local' plotter next to a dial-up
terminal and didn't need a second 'phone line, modem, host computer port,
etc.

I wonder if your machine does something like that.

The other thing is that some HP plotters were _very_ fussy about the
newline caracters being correct (if they expected CR, LF, then LF, CR did
not work). I asusme you've tried various end-of-line sequences

> explain the point of that (i.e. whether we should be trying to drive the
> thing from the terminal port or the host port).

Almost certainly the host port.

>
> Nor does it explain what the difference between 'modem' and 'hardware'
> connections are (surely the plotter knows nothing of what's actually

The behaviour of the handshake lines? 'Hardware' mode might use something
like RTS or DTR as a flow control line (it'll turn if off the plotter's
buffer gets full) but that would cause problems (like a dropped line) is
used with a real modem.

-tony
Received on Sun Jun 13 2004 - 12:21:00 BST