16.6 WPUx - Weak Pull-Up Control
The WPUx register controls the individual weak
            pull-ups for each PORT pin. When a WPUx bit is set (WPUx = 1), the weak
            pull-up will be enabled for the corresponding pin. When a WPUx bit is cleared (WPUx =
                0), the weak pull-up will be disabled for the corresponding
            pin.
