ADLINK PCI-9846 - Manual (Page 46)

36 Operation Theory
3.4.3 Analog Trigger
You can choose either CH0, CH1, CH2 or CH3 as the trigger sig-
nal while using external analog trigger source. The trigger level
can be set by software with 8-bit resolution. Please refer to
Table 3-3 for the ideal transfer characteristic.
The trigger conditions for analog triggers are illustrated in
Figure 3-9 and described 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 than the specified trigger level to a voltage that
is lower than the specified trigger level.
Trigger Level
Setting (Hex)
Trigger Voltage
(-1V to +1V Range)
Trigger Voltage
(-0.2V to +0.2V)
0xFF 0.992V 0.1984V
0xFE 0.984V 0.1968V
--- --- ---
0x81 0.0078V 1.56mV
0x80 0V 0V
0x7F -0.0078V -1.56mV
--- --- ---
0x01 -0.992V -0.1984V
Table 3-3: Ideal Transfer Characteristics for Analog Triggers