Name: National Instruments PCI-6035E
Brand: National Instruments
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Chapter 2 Theory of Operation

PCI E Series RLPM 2-18

National Instruments Corporation

Table 2-2 shows what the configuration memory should look like.

Now both channel 0 and channel 1 are sampled with 50% duty cycle.

Posttrigger and Pretrigger Acquisition

Whereas a data acquisition operation normally ends when the SC counts

down to zero, it can be initiated either through software, by strobing a bit

in a control register in the DAQ-STC, or by suitable external triggers.

There are two internal trigger lines—START1 and START2. These appear

at the connector on pins called PFI0/Trig1 and PFI1/Trig2, respectively.

START1 is used as a trigger line in the posttrigger mode. Since the START1

pulse can be generated through software by strobing a bit, all of the

examples discussed so far can be generally categorized as posttrigger

acquisition. In the classic posttrigger mode case, the data acquisition

circuitry is armed by software but does not start acquiring data until a pulse

is given on the START1 line. Then the acquisition starts and ends when the

SCAN counter counts down to zero.

In the pretrigger mode, data is acquired before and after the trigger. In this

mode, both START1 and START2 lines are used. There are two counts for

Table 2-2.

Analog Input Configuration Memory

Channel Ghost Last Channel

0 — —

1 — last channel

0 ghost —

1 ghost last channel

0 ghost —

1 — last channel

0 — —

1 ghost last channel

0 ghost —

1 — last channel

0 ghost —

1 ghost last channel

National Instruments PCI-6035E Programmer's Manual

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