When changing channel selections, the user
         should observe the following guidelines to ensure that the correct channel is selected:
- In Single Conversion mode, always
               select the channel before starting the conversion. The channel selection may be
               changed one ADC clock cycle after writing one to ADSC. However, the simplest method
               is to wait for the conversion to complete before changing the channel selection.
- In Free Running mode, always select
               the channel before starting the first conversion. The channel selection may be
               changed one ADC clock cycle after writing one to ADSC. However, the simplest method
               is to wait for the first conversion to complete, and then change the channel
               selection. Since the next conversion has already started automatically, the next
               result will reflect the previous channel selection. Subsequent conversions will
               reflect the new channel selection. 
The user is advised not to write new channel or reference selection values during Free
         Running mode.