The ADC has three different operating modes that can be selected. Single Mode performs only one conversion on only one analog input pin. If interrupts are used, the interrupt is triggered after the single conversion is done. The second mode is called Continuous Scan Mode. In this mode, the user is able to select one analog input pin or a range of pins. The ADC will then perform conversions on those pins sequentially. When all of the selected analog input pins have been converted, the ADC will start back at the first pin again. This process is continued until the ADC is told to stop. If interrupts are enabled for the ADC, an interrupt is generated every time the conversion for the last input pin has finished. The last mode is the One-Cycle Scan Mode. This mode is similar to Continuous Scan Mode except that the analog input pins are only looped through once. When the selected pins have been converted once, the ADC stops.  If the ADC interrupts are enabled then an interrupt will fire at this time.