Data Translation DT9857, User Manual, Page: 82 / 192

Chapter 5
82
Reference Trigger Sources
DT9857 and DT9857E modules support the following trigger sources for the reference trigger:
• External digital (TTL) trigger – For the DT9857 module, an external digital (TTL) trigger
event occurs when the module detects a rising- or falling-edge transition on the signal
connected to the External Trigger pin (pin 11) of the Digital connector on the module. For
the DT9857E module, an external digital (TTL) trigger event occurs when the module
detects a rising- or falling-edge transition on the External Trigger BNC input of the
module.
Using software, specify the trigger source as an external, positive digital (TTL) trigger for
a rising-edge external trigger or an external, negative digital (TTL) trigger for a
falling-edge external trigger.
• Threshold trigger – The reference trigger event occurs when the signal attached to a
specified analog input channel in the channel list rises above or falls below a
user-specified threshold value. Using software, specify the following parameters:

Reference trigger source – Specify a positive (low-to-high transition) threshold trigger
if you want to trigger when the signal rises above a threshold level, or a negative
(high-to-low transition) threshold trigger if you want to trigger when the signal falls
below a threshold level.

Threshold channel – Specify any one of the analog input channels as the threshold
input channel.

Threshold level – Specify a value between ±10 V for a gain of 1 or ±1 V for a gain of 10
as the threshold level.
Note: If you choose a threshold trigger as both the start trigger and the reference trigger,
the threshold channel and threshold level must be the same. The polarity of the trigger
(positive or negative going) can be different for each trigger source.
• Sync Bus trigger – When multiple DT9857 or DT9857E modules are connected together
using the Sync Bus (RJ45) connector, you can set the reference trigger of the analog input
subsystem of a slave module to Sync Bus if you want to receive a Sync Bus trigger from
one of the other modules to stop pre-trigger acquisition and start post-trigger acquisition.
Refer to
page 105 for more information on this configuration.