SUMMARYThis paper develops an algorithm for multiple fault diagnosis of analogue-digital circuits. By sequentially partitioning the devices into those 'assumed good' and those 'under test', it is possible to develop a set of fault diagnosis equations which account for the special nature of digital components. A modified Newton-Raphson solution is then described which incorporates a digital state hypothesis testing scheme in the solution of the fault diagnosis equations for each partition. After solving for the input-output characteristics of the devices under test, a Boolean decision algorithm is used to analyse the test results of each partition and thus sequentially arrive at the set of faulty elements. A generic condition for diagnosability in terms of the circuit topology is given. Two examples are included to illustrate the technique.