3 Sep
2004
3 Sep
'04
9:21 a.m.
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?
Waveform type? Freq range? Levels? If pulses, TTL? CMOS? Duty cycle? Rep
rate?
I need to simulate the incoming LTC signal for a system that will not be
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.
I'm planning on using a small naptha-burning steam engine driving a
modified Wimshurst static generator, and then using a calibrated spark-gap
with an RF pick-off. If I adjust the mechanical governor very precisely,
and calibrate the gap length based on humidity and barometric pressure, it
should be possible to get reasonably stable 50/60 Htz signals...
Cheers
John
PS: Please ignore the silly bits.
3 Sep
3 Sep
6:13 p.m.
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? Rep
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 be
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 spark-gap
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
6:47 p.m.
Thanks, Tony... I'm sure your catostatic generator will soon be
pur^H^H^H^H^H no, damn it, even I can't force myself to actually type a
pun *that* bad...
sorry.
Anyway, to further clarify - this particular 11/73 is destined for
(automotive) mobile roles, and therefore has had it's PSU replaced w/one
that was made quite recently, albeit for computers a few generations more
evolved than the DEC Iron. Also it is desired to be able to run the LTC at
100 Htz as well.
I am tasked with simulating the LTC signal, a simple matter, but I
haven't the actual electrical spec for this circuit, thus my question.
There will be no mains reference available.
Thanks for the fact that the LTC line is pulled up to 5V at the
terminator. That's a big chunk of the interface question out of the
way...
Cheers
Nikola Felina
6 Sep
6 Sep
9:22 a.m.
On Fri, 3 Sep 2004, John Lawson wrote:
Anyway, to further clarify - this particular 11/73
is destined for
(automotive) mobile roles, and therefore has had it's PSU replaced w/one
that was made quite recently, albeit for computers a few generations more
evolved than the DEC Iron. Also it is desired to be able to run the LTC at
100 Htz as well.
Kewl! "Powered by PDP-11" bumper stickers soon to be
available! :)
(hey Bob... you REALLY must install one of those in your truck, and
have Debee use that as a packet radio relay ;-)
I am tasked with simulating the LTC signal, a
simple matter, but I
haven't the actual electrical spec for this circuit, thus my question.
There will be no mains reference available.
Thanks for the fact that the LTC line is pulled up to 5V at the
terminator. That's a big chunk of the interface question out of the
way...
I think Qbus does fairly simple bus specs... high at 2.4V, and low at
ground to 0.4V or somesuch? Its in the Handbooks, John... those on the
shelf on your right hand side... :)
--f
5 Sep
5 Sep
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.
7419
days inactive
7422
days old
4 comments
4 participants
participants (4)
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ard＠p850ug1.demon.co.uk -
geoffreythomas＠onetel.com -
jpl15＠panix.com -
waltje＠pdp11.nl