8.1 General-Purpose I/O Lines
General-purpose I/O (GPIO) lines are managed by PIO Controllers. All I/Os have several input or output modes, such as pull up or pull down, 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 additional information, refer to the 32 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/V71devices embed high-speed pads capable of handling high-speed clocks for HSMCI, SPI and QSPI (MCK/2). Refer to the 57 Electrical Characteristics for SAM V70/V71 for additional information. Typical pull-up and pull-down 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. The following figure illustrates the On-Die Termination (ODT).
