Device and method for testing and for diagnosing digital circuits

A method for testing and for diagnosing an electrical circuit, comprising:

• (a) generating a test input signal with a word width N;
• (b) applying the test input signal to an electrical circuit to be tested, and operating the electrical circuit in a test mode so that the electrical circuit outputs at test outputs of the electrical circuit data words with a word width M in a macro clock cycle T of length L as a test response;
• and
• (c) compacting the test response output in step (b) to m compacted output signals in a micro clock cycle t with length l, where m is smaller than M and the length L is at least twice as large as the length l.

A method for designing a test apparatus for testing an electrical circuit, comprising:

• providing a test input signal generator that generates a test input signal of word width N and terminals that connect to inputs and outputs of the electrical circuit to be tested, wherein the electrical circuit includes N digital test inputs and M digital test outputs, and the terminals that connect to the test inputs of the electrical circuit are connected to receive the test input signal;
• providing a micro clock cycle t of length l and a synchronized macro clock cycle T of length L, where L is at least twice as large as 1, wherein the electrical circuit is driven such that the electrical circuit outputs data with the macro clock cycle T of length L as a test response;
• and
• providing a compactor including M inputs that are connected to the outputs of the electrical circuit to receive the test response from the electrical circuit, compact the test response with the micro clock cycle t of length l and output the test response as a data word of width m, where m is smaller than M.