Method and apparatus for all code testing

Apparatus for testing an n-bit-wide analog-to-digital converter which generates one of a set of codes, each in response to a corresponding amplitude of analog voltage applied thereto, to determine if the converter can generate all of its codes, the apparatus comprising:

• means for supplying to the converter a voltage V.sub.t and having an amplitude which varies from 0 to V volts such that the converter, when operating properly, will generate all of its codes;
• a counter for generating an n-bit count initialized at zero and which increases monotonically each time the counter is incremented, and for generating a carry bit whose state is indicative of whether the count of the counter has been incremented beyond 2.sup.n -1 which will occur when the converter is operating properly;
• a comparator for comparing the code generated by the converter to the count of the counter and for incrementing the counter when the counter count and the code produced by the device match.