Advantech PCIE-1753 User Manual page 27

The input voltage must be either higher than the minimum value of the ON state or
lower than the maximum value of the OFF state for a deterministic result. If the input
voltage is between these two values, the result is undetermined, which may be ON or
OFF. In addition, do not input a voltage higher than the maximum allowable value of
the ON state or lower than the minimum allowable value of the OFF state. The device
may be damaged under such circumstances. Refer to the device specifications for
ON and OFF state voltage ranges.
The digital input channel can also sense the status of an external switch. When con-
figured as internally pulled-up, the status of an external switch which connects the DI
terminal and the DGND terminal is sensed as shown in Figure 3.4. When configured
as internally pulled-down, the status of an external switch which is connected
between the external source and the DI terminal is sensed as shown in Figure 3.5.
Be sure the voltage of the external source is within the allowable range of the ON
state as specified in the device specifications.
Figure 3.4 Digital input signal connection using a switch as internally pulled-up
19 PCIE-1753 User Manual