The ADS1291, ADS1292, and ADS1292R have a total of two general-purpose digital input/output (GPIO) pins available in the normal mode of operation. The digital I/O pins are individually configurable as either inputs or as outputs through the GPIOC bits register. The GPIOD bits in the GPIO register control the level of the pins. When reading the GPIOD bits, the data returned are the logic level of the pins, whether they are programmed as inputs or outputs. When the GPIO pin is configured as an input, a write to the corresponding GPIOD bit has no effect. When configured as an output, a write to the GPIOD bit sets the output value.
If configured as inputs, these pins must be driven (do not float). The GPIO pins are set as inputs after power-on or after a reset. Figure 47 shows the GPIO port structure. The pins should be shorted to DGND with a series resistor if not used.