Multiplexer Settings

The MUXes are used to select input signal for each virtual channel. There are four different configuration choices that can be selected using the Channel Input mode bitfield (INPUTMODE) in the Channel Control register (CHnCTRL):

The positive and negative inputs are selected using the MUX Positive Input and MUX Negative Input bitfields (MUXPOS and MUXNEG) in the Channel MUX Control register (MUXCTRL). An alternative name for the MUX Positive Input bitfield used in the header files is MUX Internal Input (MUXINT) when measuring internal inputs.

In devices with two ADCs, the inputs can only be connected to the corresponding port. Meaning that ADC A can be connected only to PORT A, and ADC B can be connected only to PORT B. The positive input can be connected to anyone of the eight input signals of the corresponding port. The negative input can be connected to one of the first four input signals (PIN0 – PIN3) of the corresponding port for differential without Gain and the second four input signals (PIN4 – PIN7) for differential with Gain.

In devices with only one ADC but several analog ports, the positive input can be connected to any of the available input signals from both PORT A and PORT B. The negative input can be connected to one of the first four input signals (PIN0 – PIN3) of the corresponding port for differential without Gain and the second four input signals (PIN4 –PIN7) for differential with Gain.

Refer to the data sheet to determine the number of ADCs and the devices pin configuration.
Note: The sampling capacitor is drained between each sample for all modes except for differential mode with gain. In the differential mode with gain, the charge on the sampling capacitor is maintained and this can be used to get a higher sample rate on slow changing signals. This can be used to get higher sampling rates on high impedance sources compared to single channel or differential channel (without gain) sampling. This will, however, propagate to other channels if the sample rate is too high compared to the source impedance.