ADLINK PCI-9820 - Manual (Page 35)

Operation Theory
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0x01 -4.96V -0.992V
Table 4.1 Analog trigger ideal transfer characteristic
The trigger conditions for analog triggers are illustrated in Fig4.8 and de-
scribed as follows:
• Positive-slope trigger - The trigger event occurs when the trigger
signal (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 trigger
signal (analog input signal) changes from a voltage that is higher then the
specified trigger level to a voltage that is lower than the specified trigger level.
Figure 4.8 Analog trigger conditions
4.4.3 External Digital Trigger
An external digital trigger occurs when a TTL rising edge or a falling edge is
detected at the SMB connector TRG IO on the front panel, as illustrated in Fig
4.9. The trigger polarity can be selected by software. Note that the signal
level of the external digital trigger signal should be TTL-compatible, and the
minimum pulse width is 10ns.
The TRG IO on the front panel can also be programmed to output the trigger
signal when the trigger source is from software, analog trigger, or SSI trigger.
The timing characteristic is in Fig 4.10.
Negative-slope trigger event
occurs
Positive-slope trigger event
occurs