The D1700 series modules may be setup in special modes which allow them to communicate without being polled by a host computer. Collectively these modes are called Continuous Input/Output Modes. In many applications the burden on the host may be greatly simplified and in some cases the host may be eliminated altogether. Three modes are available:
1. Timer Mode: In this mode, a software timer is activated in the module with the Continuous Timer (CT) command. The CT command specifies a time period that repeats indefinitely. After each timeout, the module will output the status data. The module will periodically output the digital input data until the continuous mode is disabled.
2. Edge-Trigger Mode: In this mode the D1711/1712 will output a data string when it receives a trigger signal on the B00/EV I/O Pin. The edge trigger mode will produce an output in response to an external event. It also provides a means of daisy-chaining several continuous output modules together.
3. Change Mode: In this mode the D1711/1712 continuously monitors the status of the I/O lines. If a change is detected in status, an output data message is initiated.