Pins are general purpose I/Os (GPIOs) with the exception of PIN2, which only serves as a digital input. Certain pins have unique properties. Pin 2 can be configured as a chip reset. Pins 8 and 9 are designated for the SCL and SDA lines of the I2C interface. If I2C interface is not needed, pins 8 and 9 can be used as general purpose IO, but only as an open-drain NMOS output. Pins 8 and 9 have no PMOS structure, and thus cannot be configured as a push-pull output. However this allows pins 8 and 9 to be pulled above VDD without being limited by internal diode clamping. Analog I/O are limited to certain pins, and depend on the macro-cell used (see macro-cell help info for connectivity information).
Set ‘I/O selection’ to a GPIO mode that is not ‘Pin not Used’.
Alternatively, drag a wire to or from the PIN and a signal.
For Digital Input/Output signals, connect the OE pin to an I/O control signal.
Select the GPIO mode using ‘I/O Selection’. The table show the GPIO Pad level (High, Low, Hi-Z or Analog).
Push Pull outputs cannot be configured with a PU or PD Resistor.
4X drivers are stronger than 2X drivers which are stronger than 1X drivers; sourcing more current. However, the time it takes to drive an output is inversely longer.
Digital Inputs, if left floating, will leak current; tie them to a rail.
Use Schmitt triggers to debounce high frequency input signals.
Table 1. GPIO Pad
| I/O selection | OE | IO mode | GPIO Pad | Resistor |
|---|---|---|---|---|
| Pin not Used | 0 | w/o Schmitt trigger | Z | 1M Pull Down |
| Digital Input | 0 | w/o Schmitt trigger | Z | — |
| w/ Schmitt trigger | Z | — | ||
| Low Voltage DI | Z | — | ||
| Digital Output | 0 | 3-state Output | Z | — |
| 1 | Push Pull | H/L | Floating | |
| Open Drain NMOS | Z/L | — | ||
| Open Drain PMOS | H/Z | — | ||
| 3-state Output | H/L | — | ||
| Analog Input/Output | — | Analog Input/Output | — | — |
| Digital Input/Output | 0 | w/o Schmitt trigger | Z | — |
| w/ Schmitt trigger | Z | — | ||
| Low Voltage DI | Z | — | ||
| 1 | Push Pull | H/L | Floating | |
| Open Drain NMOS | Z/L | — | ||
| Open Drain PMOS | H/Z | — |
Legend
H = High
L = Low
Z = Hi-Z
A = Analog Voltage
Add a Pull Up or Pull Down resistor on the GPIO. Pin not Used has a 1M Pull Down. Push Pull outputs cannot be configured with a Pull Up/Pull Down Resistor. All ports are in Hi-Z state until chip is powered up. Use the quick charge mode, see Power Ctrl Settings, to quickly charge pins to an initial state when power to device is applied.
• Pull down resistor: Default low
• Pull up resistor: Default high
• Floating: no resistor
‘Resistor’ must be ‘Pull up’ or ‘Pull down’. Resistor value (in ohms) of 10K, 100K or 1M can be chosen. Default is 1M.
V_IH is the input voltage at digital signal transitions from a low to high.
V_IL is the input voltage at digital signal transitions from a high to low.
V_OH is the output voltage at digital high.
V_OL is the output voltage at digital low.
I_OH is the output current at digital high.
I_OL is the output current at digital low.