The ADS1291, ADS1292, and ADS1292R input multiplexers are very flexible and provide many configurable signal-switching options. Figure 18 shows the multiplexer for the ADS1291, ADS1292, and ADS1292R. Note that TESTP, TESTM, and RLDIN/RLDREF are common to both channels. INP and INN are separate for each of the three pins. This flexibility allows for significant device and sub-system diagnostics, calibration, and configuration. Switch settings for each channel are selected by writing the appropriate values to the CH1SET or CH2SET register (see the CH1SET and CH2SET Registers in the Register Maps section for details). More details of the ECG-specific features of the multiplexer are discussed in theInput Multiplexer subsection of the ECG-Specifc Functions.