Hi John:
Yes RTL and 3.3 V if I remember correctly.
Have Fun,
Brooke Clarke
http://www.PRC68.com
jmfranke wrote:
Wasn't that a RTL 923 and 914? I still have a few from my learning days.
John WA4WDL
--------------------------------------------------
From: "Brooke Clarke" <[email protected]>
Sent: Thursday, April 15, 2010 11:24 AM
To: "Discussion of precise time and frequency measurement"
<[email protected]>
Subject: Re: [time-nuts] lunatic fringe time standards
Hi Didier:
When working with high speed data, for example an IDE hard drive,
where there are parallel data lines you get into the same problem as
you have with a shaft encoder where there are parallel binary data
lines. In the case of the shaft encoder mechanical misalignment can
cause huge errors at the transitions and in the hard drive jitter and
time delays can cause similar problems. I think that was one of the
main motivations to go to a serial hard drive interface (SATA).
When in college I used a Johnson counter made from the first ICs from
Fairchild, i.e. the 723 flip-flop and the 714 two input gate. The
beauty of the Johnson counter is that you can decode it's state with
ten each two input gates.
http://www.prc68.com/I/comp.shtml#Nixie
Have Fun,
Brooke Clarke
http://www.PRC68.com
Didier Juges wrote:
I believe Gray code was invented to support absolute mechanical
position encoders, where the speed of the electronics is high
compared to the speed of the hardware being monitored. It eliminates
the potentially large error between two positions since only one bit
changes at a time. This is done at the expense of complicated logic,
which goes against speed.
I don't think Gray code has ever been used to implement fast
electronic counters. That's what synchronous counters are for, and
when synchronous counters are not fast enough, use a prescaler. It
will just take more time to get the precision you need.
Unless you need fractional Hz resolution at THz speed, a prescaler
is the way to go.
Didier
------------------------ Sent from my BlackBerry Wireless thingy
while I do other things...
-----Original Message-----
From: Eugen Leitl<[email protected]>
Date: Thu, 15 Apr 2010 13:42:00
To:<[email protected]>
Subject: Re: [time-nuts] lunatic fringe time standards
On Thu, Apr 15, 2010 at 07:30:27AM -0400, Bob Camp wrote:
Hi
I'm not 100% sure I understand exactly what you are thinking about
setting up.
This is completely theoretical at this point. Just the required
geometry
size would be prohibitive.
My guess is that the counter needs to run at the same THz speed as
the oscillator. That's pretty fast. I suspect that what ever you use,
speed / propagation delay in the counter it's self will be an issue.
That will get you back to either a ripple counter or a Johnson
counter.
Wouldn't you get large errors when you caught a ripple
during readout? That wouldn't be a problem with a Gray code.
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