5 Sep
2004
5 Sep
'04
6:17 p.m.
----- Original Message -----
From: "Tony Duell" <ard(a)p850ug1.demon.co.uk>
To: <cctalk(a)classiccmp.org>
Sent: Saturday, September 04, 2004 12:13 AM
Subject: Re: LTC Spec question
Rep
be
spark-gap
W/out having the docs to hand, I would like to know the actual
electrical specification for the LTC line as implemented in LSI-11 -type
systems... what is the backplane (and hence the CPU, etc) expecting?
I've looked at the PSU schemmatics for my MINC, which should be close
enough...
>
> Waveform type? Freq range? Levels? If pulses, TTL? CMOS? Duty cycle? rate?
Waveform : Square wave
Frequency : Mains frequency (50Hz or 60Hz), duty cycle doesn't seem to
matter.
Open collector driver (pulled up in the bus terminator to +5V)
>
> I need to simulate the incoming LTC signal for a system that will not > mains powered.... in the older 11/xx systems,
this was derived from one
of
the windings
of the power supply transformer, then made into
line-freq-rate pulses by the using module.
That's how it's done in the MINC (and in the LSI11/03 prints I looked at
which show the H780 PSU). The Minc uses one section of a 339 comparator
chip connected to the secondary of a mains transformer through a suitable
resistor netowrk.
>
>
> I'm planning on using a small naptha-burning steam engine driving a
> modified Wimshurst static generator, and then using a calibrated
I always prefered the catostatic.
[OK, a joke. I have a book on making electrostatic generators and one of
them is called the catostatic. As you may have guessed by now, this
involves stroking your cat and collecting the accumulated charge in a
Leyden jar... Knowing my cat, he'd probably get rather fed up with the
whole idea...]
-tony
I rather like old Lord Kelvin's dripping water e/s generator myself - really
has an impact when demonstrated to children - electric charge from dripping
water.
Geoff.