2.3 Buffer Types
| Buffer | Description |
|---|---|
| AI | Analog input |
| AIO | Analog bi-directional |
| ICLK | Crystal oscillator input |
| OCLK | Crystal oscillator output |
| PU | 55kΩ (typical) internal pull-up. Internal pull-up resistors prevent unconnected inputs from floating. Do not rely on internal resistors to drive signals external to the device. When connected to a load that must be pulled high, an external resistor must be added. |
| VI-VDDAU | 3.3V input (VDDAU continuous power domain) |
| VIS-VDDP | 3.3V Schmitt-triggered input (VDDP power domain) |
| VO-VDDP | 3.3V output with configurable output drive (VDDP power domain) |
| VOH-VDDP | 3.3V high-speed output with configurable output drive (VDDP power domain) |
| VODL-VDDP | 3.3V N-channel open-drain sink output drive (VDDP power domain) |
| VODH-VDDAU | 3.3V P-channel open-drain source output drive (VDDAU power domain) |
Note: Digital signals are not 5V tolerant.