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DaqBoard/500 Series 988994 Software and Board Operation 4-5
Starting (Triggering) an ADC Acquisition
There are several methods that can be used to initiate an acquisition, all of these are achieved by triggering or gating
the ADC clock as mentioned previously. Note that a trigger is an edge active event and a gate is a level controlled
enable.
An acquisition can be initiated via the following:
o Software
o External Gate (ADTRGIN)
o External Trigger (ADTRGIN)
ADC Software
Software can be used to start and stop the on-board ADC pacer clock.
ADC External Gate
An ADC clock may be “switched On” (and Off) with the external ADTRGIN input. The input is level sensitive and
selectable as either active high or active low control. If the on-board pacer clock drives the ADC, the external gate
input is used to enable and disable the ADC’s pacer clock after being polarity conditioned. The ADC clock will be
enabled as long as the gate input is in the active state.
ADC External Trigger
The external gate/trig input (ADTRGIN) may also be configured as a rising or falling edge sensitive input to trigger
the start of the ADC clock. External triggers are ignored until the ADC is enabled. Once the ADC is enabled, the
next active edge signal on ADTRGIN will enable the ADC Clock source. To disable the clock, refer to the
following section, Stopping an ADC Acquisition (CLOCK).