dkelvey at hotmail.com
Thu Feb 25 00:32:43 CST 2010
> Date: Wed, 24 Feb 2010 18:28:43 -0800
> From: hilpert at cs.ubc.ca
> To: cctalk at classiccmp.org
> Subject: Re: Nicolet DSO
> I opened up the Nicolet 2090-III DSO at the radio museum last week. There were
> no 9900 micro-procs (no I/O options I guess), I am somewhat surprised the basic
> scope seems to be done with dedicated logic. Three 2901 bit-slices, two Analog
> Devices ADC-80's (IIRC) for the A-D, bank of 2141's (nic) for RAM, some ROM's I
> think, and a lot of SSI/MSI. Date codes early 80's.
> The electronics may be interesting for the period, but as with other Nicolet
> equipment I have seen, the physical design is horrible in regards to
> accessibility and maintenance. Major portions of logic are buried and
> inaccessible without tortured dismantling.
As I call it a puzzle box.
> Fired it up, seems to work for capturing sine wave from finger on input. Still
> have to figure out some of the functions. I take it the 1H, 2H, 1Q, 2Q, etc.
> modes are for recording in interleaved halves or quarters of memory? Do you
> know if the SUB function subtracts a new sweep from the currently active
> memory, or does it operate on two portions of already-recorded memory?
It processes data in menory. Which it uses depends on where the memory switch
is. It also records the two input channels in the two halves when the memory
is set to all.
The following are valid memory settings for subraction:
Q3 Q1-Q3 into Q3
Q2 Q4-Q2 into Q2
Q4 Q2-Q4 into Q4
H1 H2-H1 into H1
H2 H1-H2 into H2
All No effect
The memory is 4K total. Each quarter is 1K. When recodrding
differential, one channel goes to H1 and the other H2 with
The invert allows one to add to by first inverting and then
With the disk system that mine has, I can recall previous
recodered results and do math on them.
The one thing I found offensive has to do with the Pin operation.
This sends the screen info to a XY plotter. The problem I found
is that in order to use the memory effectively in XY mode for
my analog computer, I need to do sparce sampling. When doing
the pen mode, it does a square move from dot to dot. In other
words, it does the move in one axis and then moves in the other axis.
For the sparce sampling that I have it make the plotting
worthless. I'd have thought that with the 2901's, it could
have done the math to draw lines between the dot.
It is still quite useful. When doing long runs, I can visualize
exactly what I'm doing.
Also, I can use the horizontal or vertical magnification to
balance the gain and decay such that the sine/cosine
generators don't decrease or increase in amplitude over the
time spans I need to run a plot on my XY plotter.
For these things it is just what I wanted.
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