General-purpose (GPIO) lines are managed by PIO Controllers. All I/Os have several input or output modes such as pullup or pulldown, input Schmitt triggers, multi-drive (open-drain), glitch filters, debouncing or input change interrupt. Programming of these modes is performed independently for each I/O line through the PIO controller user interface. For more details, refer to Parallel Input/Output Controller (PIO).
The input/output buffers of the PIO lines are supplied through VDDIO power supply rail.
The SAM E70/S70/V70/V71 embeds high-speed pads able to handle the high-speed clocks for HSMCI, SPI and QSPI (MCK/2). Refer to Electrical Characteristics for SAM V70/V71 for more details. Typical pullup and pulldown value is 100 kΩ for all I/Os.
Each I/O line also embeds a RSERIAL (On-die Serial Resistor), as shown in the following figure. It consists of an internal series resistor termination scheme for impedance matching between the driver output (SAM E70/S70/V70/V71) and the PCB trace impedance preventing signal reflection. The series resistor helps to reduce I/Os switching current (di/dt). thereby reducing in turn, EMI. It also decreases overshoot and undershoot (ringing) due to inductance of interconnect between devices or between boards. Finally, RSERIAL helps diminish signal integrity issues.
