Searching \ for '[PIC] Oscilloscopes???' in subject line. ()
Make payments with PayPal - it's fast, free and secure! Help us get a faster server
FAQ page: www.piclist.com/techref/microchip/devices.htm?key=pic
Search entire site for: 'Oscilloscopes???'.

Exact match. Not showing close matches.
PICList Thread
'[PIC] Oscilloscopes???'
1996\04\29@013008 by Xaq

flavicon
face
Does any one know how the horizontal retrace (trigger) works on an
oscilloscope?  If you just use level triggering then how can you stabilize a
digital signal like this one:

     ____     ____              ____     ____
    |    |   |    |            |    |   |    |
    |    |   |    |            |    |   |    |
_____|    |___|    |____________|    |___|    |________


sometimes it would trigger off of the first pulse and sometimes of off the
second.  This would cause the wave to jump around.  I have used an analog
scope were this signal is rock solid.  How does it work?

Zach

1996\04\29@140604 by Martin J. Maney

flavicon
face
On Sun, 28 Apr 1996, Xaq wrote:

> Does any one know how the horizontal retrace (trigger) works on an
> oscilloscope?  If you just use level triggering then how can you stabilize a
> digital signal like this one:
>
>       ____     ____              ____     ____
>      |    |   |    |            |    |   |    |
>      |    |   |    |            |    |   |    |
> _____|    |___|    |____________|    |___|    |________
>
>
> sometimes it would trigger off of the first pulse and sometimes of off the
> second.  This would cause the wave to jump around.  I have used an analog
> scope were this signal is rock solid.  How does it work?

The key is "hold off": the trigger circuit ignores edges during the
sweep, of course, and in better scopes for a controllable time after the
active part of the sweep is finished as well.  In fact, a waverform like
the above may or may not sync solidly: it depends on the relationship
between the waveform's periodicity and the period from the trigger that
begins the sweep until the time when the trigger circuit is once more "live".

Does this make sense?  What you need for that signal is to make the
active sweep period (plus any hold off) such that the trigger does NOT
see the wrong rising edge when it's active.  The jumping around you
describe can happen with an analog 'scope too...

1996\04\29@161003 by Eric Strauts

flavicon
face
Zach,

After the oscilloscope sweep ends there is sometimes a variable delay
time called the "holdoff" period. This is usually a control knob. By
adjusting the holdoff time you can wait until the second pulse in the
train has passed and the next signal that triggers the following
sweep will then be the first pulse.

If there is no sweep holdoff control you can also adjust the sweep
vernier control to make the length of the sweep such that it displays
an integral number of pulse groups. Again the first pulse following
the end of the sweep can be made to be the first pulse in the group.

-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*
| Eric Strauts                         |
| TEEM Electronics                     |
| Park Ridge, IL 60068                 |
| Email: spam_OUTestrautsTakeThisOuTspamix.netcom.com        |
-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*-*

1996\04\29@190332 by Ken Parkyn

flavicon
picon face
>Does any one know how the horizontal retrace (trigger) works on an
>oscilloscope?  If you just use level triggering then how can you stabilize a
>digital signal like this one:
>
>      ____     ____              ____     ____
>     |    |   |    |            |    |   |    |
>     |    |   |    |            |    |   |    |
>_____|    |___|    |____________|    |___|    |________
>
>
>sometimes it would trigger off of the first pulse and sometimes of off the
>second.  This would cause the wave to jump around.  I have used an analog
>scope were this signal is rock solid.  How does it work?
>
>Zach
>
If the signal is data, it'll dance around anyway...
If the signal is repetitive, you should be able to lock to it by
synchronising your cro with the clk2 output of the PIC

my tuppence worth
Cheers,
Ken Parkyn
Grandma always said: "Don't eat blue food"

More... (looser matching)
- Last day of these posts
- In 1996 , 1997 only
- Today
- New search...