The difference between analog and digital triggers is the difference in trigger source. A digital trigger is a TTL signal that is used as the starting point for the acquisition on either the rising or falling edge. The following figure shows the falling edge trigger.
Figure 1. Digital Trigger
In contrast, an analog trigger can trigger an acquisition using a variety of methods, such as a rising and falling analog edge, an analog window, a hysteresis rising and falling analog edge.
For analog edge triggering, trigger with a specific signal level and slope. It is used to set the device to find a specific signal level and slope (rise or fall). The following figure, the trigger is set to acquire data from the rising edge signal when the signal reaches 3.2V.
Figure 2. Analog edge trigger
For hysteresis analog edge triggering, It is often used to reduce false triggering in signals caused by noise or jitter. When hysteresis is used at a rising slope, the trigger occurs when starting under Level-Hysteresis and crossing over Level. The trigger is released when the signal passes below the Level-Hysteresis. like the Figure 3.
Figure 3. Hysteresis with rising slope
When hysteresis is used at a falling slope, the trigger occurs when starting above Level+Hysteresis and crossing under Level. The trigger is released when the signal passes above the Level+Hysteresis. like the Figure 4.
Figure 4. Hysteresis with falling slope