The AUX GPIO path is the same as the main GPIO path. All eight GPIOs are multiplexed to a single AUX ADC MUX input. There is only one GPIO slot in the AUX ADC round robin cycle. That is, in a single AUX ADC round robin cycle, only one GPIO will be measured. To complete all eight GPIO measurements, it takes eight round robin cycles. If GPIO is connected to the thermistor network, the MCU enables TSREF by setting CONTROL2[TSREF_EN] = 1 and ensures TSREF is stable before starting the AUX ADC measurement.

When AUX ADC is enabled, the GPIO slot in the 1st round robin cycle is GPIO1, 2nd round robin cycle is GPIO3, and so on. For the AUX ADC to make a measurement on a GPIO, the GPIO must be configured as ADC input in the corresponding GPIO_CONFn[GPIO*2:0] bits, where n = 1 to 4, * = 1 to 8 for the respective GPIO channel. See Section 8.3.4 for more details. If the GPIO is inactive for the ADC measurement, the device ignores the corresponding GPIO slot but does not remove the slot from the AUX ADC round robin cycle.

By default, the AUX ADC loops through all GPIO channels and the measurements do not report out to the result registers. However, if MCU locks to a single GPIO channel, the locked GPIO measurement is reported to the AUX_GPIO*_HI (high-byte) and AUX_GPIO*_LO (low-byte) registers. This channel lock can be set by the ADC_CTRL3[AUX_GPIO_SEL3:0] bits. The result registers will report a GPIO measurement if [AUX_GPIO_SEL3:0] is locked to single GPIO channel, any other condition will show default value 0x8000.

Figure 8-8 GPIO Slot with Different [AUX_GPIO_SEL3:0] Setting