Added a proper channel mapping doc. There is very strange behavior with the device when trying to run an impedance test. Basically, the data registers are always saturated (contain all 0's or 1's). I am not sure if this is a read issue. When I try to read back the chip configuration, some of the configuration bits are not what I set them to. For instance, the external clock cannot be specified currently. This is strange because I have no trouble specifying voltage, freq, etc.