19.5 ANSELx - Analog Control

Ports that support analog inputs have an associated ANSELx register. The ANSELx register is used to configure the Input mode of an I/O pin to analog. Setting an ANSELx bit high will disable the digital input buffer associated with that bit and cause the corresponding input value to always read ‘0’, whether the value is read in PORTx register or selected by PPS as a peripheral input.

Disabling the input buffer prevents analog signal levels on the pin between a logic high and low from causing excessive current in the logic input circuitry.

The state of the ANSELx bits has no effect on digital or analog output functions. A pin with TRIS clear and ANSEL set will still operate as a digital output, but the Input mode will be analog. This can cause unexpected behavior when executing Read-Modify-Write instructions on the PORTx register.