Starts A/D conversion.
Remark         
About 1 micro second of stabilization time is required when changing the voltage 
converter from operation stopped to operation enabled status.
Consequently, 
about 1 micro second must be left free between the call to R_ADC_Set_OperationOn and the call to this API 
function.
[Syntax]
void R_ADC_Start ( void );
[Argument(s)]
None.
[Return value]
None.