Chapter 4 The Instruction Trigger Function; Internal Trigger Mode; External Trigger Mode - Beijing ART Tech PCI8757 User Manual

PCI8757 Data Acquisition

Chapter 4 The Instruction Trigger Function

4.1 Internal Trigger Mode

When A/D is in the initialization, if the A/D hardware parameter ADPara.TriggerMode = PCI8757_TRIGMODE_SOFT,
we can achieve the internal trigger acquisition. In this function, when calling the StartDeviceProAD function, it will
generate A/D start pulse, A/D immediately access to the conversion process and not wait for the conditions of any other
external hardware. It also can be interpreted as the software trigger.
As for the specific process, please see the figure below, the cycle of the A/D work pulse is decided by the sampling
frequency.
Start Enable
Convert Pulse
The first working
pulse after the A/D
start pulse

4.2 External Trigger Mode

When A/D is in the initialization, if the A/D hardware parameter ADPara.TriggerMode = PCI8757_TRIGMODE_POST,
we can achieve the external trigger acquisition. In this function, when calling the StartDeviceProAD function, AD will
not immediately access to the conversion process but wait for the external trigger source signals accord with the
condition, then start converting the data. It also can be interpreted as the hardware trigger. Trigger source includes the
DTR (Digital Trigger Source) and ATR (Analog Trigger Source)
The trigger modes include the edge trigger and level trigger.
(一) ATR Trigger
ATR
Comparer
Trigger Level
Figure 4.2 Analog compare
Figure 4.1 Internal Trigger Mode
Result
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