TM4C123GXL GPIO - Disable Analog function

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GPIO - Analog function

If any pin is to be used as an ADC input, the appropriate bit in the GPIOAMSEL register must be set to disable the analog isolation circuit. To enable GPIO pins to their analog function (if available), set the GPIOAMSEL bit in the GPIOAMSEL register.

Tm4c analog digital io pads.png

GPIO Analog Mode Select (GPIOAMSEL)

The GPIOAMSEL register controls isolation circuits to the analog side of a unified I/O pad. Because the GPIOs may be driven by a 5-V source and affect analog operation, analog circuitry requires isolation from the pins when they are not used in their analog function. Each bit of this register controls the isolation circuitry for the corresponding GPIO signal.

Important: This register is only valid for ports and pins that can be used as ADC AINx inputs.

Tm4c gpioamsel r.png
Bit/Field Name Description
7:0 GPIOAMSEL GPIO Analog Mode Select
0: The analog function of the pin is disabled, the isolation is enabled, and the pin is capable of digital functions as specified by the other GPIO configuration registers.
1: The analog function of the pin is enabled, the isolation is disabled, and the pin is capable of analog functions.
31:8 Reserved Software should not rely on the value of a reserved bit.