The Input/Output Pins (I/O PINS) are for receiving external signals and sending signals out. These general purpose I/Os (GPIOs), can be configured as Analog and Digital inputs and outputs with the exception of PIN2 which can only serve as a digital input or external reset. PINs 4, 5, 6, 10, 11, and 12 can be used as a 3-state Output or Input and Output in the same design.
Different mode selections per pin can have different restrictions on input/output types.
• Digital input with Schmitt Trigger: configures the PIN to have hysteresis which rejects fast and spurious signal transitions;
• Digital input without Schmitt Trigger;
• Low voltage digital In: the voltage threshold which determines HIGH from LOW is lower than in regular Digital input mode. Use Low voltage digital Input if a desired function is to sense low voltage logic levels (for example 1.8V input signals if the chip VDD is 3.3V or 5V);
• Analog In
• 1x push pull
• 2x push pull
• 1x open drain
• Analog In and Open Drain out
Available for both Input and Output. All ports are in Hi-Z state until chip is powered up. In case of PIN 2, the resistors are fixed to a pull-down configuration only. In case of all other I/O PINs, the internal resistors can be configured as either pull-ups or pull- downs.
• Pull down resistor: Default low;
• Pull up resistor: Default high;
• Floating: no resistor;
If a Pull up or Pull down resistor was chosen for the Resistor parameter, there are three selectable resistor values.
• 50k strongest pull up/down;
• 100k medium pull up/down;
• 300k weakest pull up/down;
At power on reset (POR), the initial state of each PIN can be configured. Those configurations are either GND, VDD, floating or following the input.