ADLINK PCI-9527 - Manual (Page 44)

32 Operation Theory
PCI-9527 ADLINK Technology Inc.
User’s Manual Copyright 2010
External Digital Trigger
An external digital trigger occurs when a TTL rising edge or a fall-
ing edge is detected at the SMB connector on the front panel. As
illustrated in Figure x-x, the trigger polarity can be selected by soft-
ware. Note that the signal level of the external digital trigger signal
should be TTL compatible, and the minimum pulse width is 25 ns.
Analog Trigger
User can configure the PCI-9527 analog trigger circuitry to monitor
one of analog input channels from which you acquire data. Select-
ing an analog input channel as the analog trigger channel does not
influence the input channel acquisition operation. The analog trig-
ger circuit generates an internal digital trigger signal based on the
condition between analog signal and the trigger level you defined.
The trigger conditions for analog triggers is described as follows:

Positive-slope trigger: The trigger event occurs when the
analog input signal changes from a voltage that is lower
than the specified trigger level to a voltage that is higher
than the specified trigger level.
 Negative-slope trigger: The trigger event occurs when the
analog input signal changes from a voltage that is higher
than the specified trigger level to a voltage that is lower than
the specified trigger level.
Figure 3-3: Analog Trigger Conditions
Trigger Level
Positive-Slope Trigger Event
Occurs
Negative-Slope Trigger
Event Occurs
Analog
Signal