Neurotechnology Research Systems
© Plexon Inc
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7.7
Trigger Options
There are three ways to initiate stimulation: Software, Edge Digital Input, and Level Digital Input.
In all cases, the stimulation pattern for the channel must be defined before it can be triggered.
7.7.1
Software Triggering
Stimulation can be initiated by clicking on the Start or Start All buttons in the GUI or calling one of
the start functions in the SDK. Each time Start or Start All is pressed, the stimulation pattern for the
channel is initiated.
7.7.2
Digital Input Triggering
7.7.2.1
Edge Triggering
In the Edge trigger mode, stimulation begins when the Start digital input for the channel transitions
from low (~0V) to high (~5V) if DI Polarity is set to Positive. If DI polarity is set to Negative,
stimulation begins when the digital input transitions from high to low. The latency from digital
input to stimulation onset is less than 10 µs for the first channel that is started. Since all channels
are timed from the same 10 kHz clock, there is a 100µs variability when starting subsequent
channels. This is because they will not start until the next 10 kHz clock edge comes following the
digital input. Stopping stimulation also has a 100 µs variability because the pulse cannot end until a
10kHz clock edge is seen.
Once the stimulation pattern is triggered it will play to completion even if the Start digital input
goes low during the stimulation. The pattern can be stopped by a rising edge on the Stop digital
input.
7.7.2.2
Level Triggering
In the Level trigger mode, stimulation also begins when the Start digital input for the channel
transitions from low (~0V) to high (~5V) when DI Polarity is set to Positive and continues until the
Start digital input goes low again. The reverse is true if DI Polarity is set to Negative. The Stop
digital input is not used in Level triggered mode.
7.7.2.3
DI Polarity Positive
If DI Polarity is set to Positive and the device is in Edge triggered mode, the controller responds to
rising edges on the digital input start and stop pins. In Level triggered mode, the controller starts
on a rising edge of the Start digital input and stops on a falling edge of the Start digital input. Note
that changing polarity while a channel is loaded may cause it to start immediately depending on the
current state of the digital input. If a digital input is at 0V and the polarity is changed from positive
to negative, stimulation will start.