Finally, here is a quick look at the RL78 AD converter’s diagnostic functions. Users can use the diagnostics function to test if the sample-and-hold circuit is stuck at a specific value. This is done using the special input selector which allows ground, VDD, or an internal or external reference to be connected to the sample-and-hold circuit. Thus the sample-and-hold circuit can be checked and even the AD converter can be checked to determine if it is still in the proper range. For example if the sample-and-hold circuit starts at zero, 0xFF or somewhere else.