Resolver/digital converter and control apparatus using the same

This resolver/digital converter has a resolver (5), a resolver/digital converting portion (2) and an exciting signal generator (3). The exciting signal generated from the exciting signal generator (3) is supplied to the resolver (5), and the resolver signals produced from the resolver (5) are supplied to the resolver/digital converter (2). This resolver/digital converter further has a conversion trigger generator (4) that generates a conversion trigger signal on the basis of the exciting signal generated from the exciting signal generator (3), an A/D converter (11) that converts the resolver signals produced from the resolver (5) to digital values in response to the conversion trigger signal generated from the conversion trigger generator (4), and computing means (12) that detects the failure status on the basis of the digital values produced from the A/D converter (11).