Changing Trigger Values

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mnaylor3
Posts: 7
Joined: Tue Mar 23, 2010 7:36 pm
Location: San Antonio, TX

Changing Trigger Values

Post by mnaylor3 » Wed Apr 20, 2011 8:47 pm

Hi Guys,

We've been recording ERPs using Presentation. New trigger codes show up ever so often. It's puzzling.

Here is one coding system we have:

1
2
100
200
9
10

Sometimes, these codes show up:

110
91

Our programmer says that, for some reason, codes are being added together or subtracted.

110=100+10
91=100-9

Does this have something to do with ActiView?

Coen
Site Admin
Posts: 969
Joined: Fri Mar 26, 2004 7:00 pm
Location: Amsterdam, Netherlands
Contact:

Post by Coen » Thu Apr 21, 2011 4:14 pm

In general, use the following guidelines to solve trigger problems:

- Use the "analog" trigger display to display the trigger lines bit by bit, colored dots and bars indicate High trigger lines
- Ensure that positive logic is used (Low = no-trigger, High = trigger)
- Return all trigger lines to Low after each trigger
- Inspect the trigger lines for increasing codes. For example: 1 = only trig line one shows dot, 5 = trigger lines 1 and 3 shows dots, etc
- Ensure that for a given trigger code, all relevant bits go High and Low simultaneously (within one sample period). If not, a trigger code will be displayed as several (other) successive codes.

Best regards, Coen (BioSemi)

Aliez
Posts: 4
Joined: Wed Dec 15, 2010 8:02 pm
Location: Boston

Post by Aliez » Sat Jun 18, 2011 5:02 pm

Hi Coen,

I found this post related to my problem that I posted yesterday.
In addition to my previous questions, can you please explain your reply to this post a little bit more?

What does positive logic mean? & what do you mean by returning trigger lines to low after each trigger? how should we do it? (can you please provide examples)

how could we ensure that for a given trigger code, all relevant bits go High and Low simultaneously?

Thank you.
Regards
Ali

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