\section{Digital Input Unit}

The digital input unit is the input counterpart of the digital output unit. 

In addition to reading the immediate digital levels of the selected pins, this unit can generate asynchronous events on a pin change. The state of the entire input port, together with a microsecond timestamp (as is the case for all asynchronous events), is reported to the host either on a rising, falling, or any pin change. 

The pin change event can be configured independently for each pin. In order to receive a pin change event, it must be armed first; The pin can be armed for a single event, or it may be re-armed automatically with a hold-off time. It's further possible to automatically arm selected pin triggers on start-up.