AD CONVERTER AND DATA PROCESSING UNIT

An AD converter includes an input circuit, an operation circuit and a bus interface. The input circuit is provided with a pull-down circuit, which is capable of pulling down an analog signal input side of a sample-hold circuit whether an analog signal is inputted or not. The operation circuit is provided with a reference voltage conversion result storing register, which is capable of storing a conversion result of an analog reference voltage inputted periodically separately from a conversion result of the analog signal inputted through the sample-hold circuit. The operation circuit is further provided with a check register, which is capable of writing in and reading out data for checking operation of a signal transfer system including a bus interface through the bus interface. Thus, it is made possible to confirm normality of an external part and an internal part of the AD converter.