Abstract: An electronic circuit contains groups of flip-flops (12a-c), coupled to data terminals (11a-c) of the circuit and to a functional circuit (10). Each group (12a-c) has a clock input for clocking the flip-flops of the group. Each group (12a-c) can be switched between a shift configuration and a functional configuration, for serially shifting in test data from the data terminals and to function in parallel to supply signals to the functional circuit (10) and/or receive signals from the functional circuit (10) respectively. A test control circuit (16) can be switched between a functional mode, a test shift mode and a test normal mode. The test control circuit (16) is coupled to the groups of flip-flops (12a-c) to switch the groups to the functional configuration in the functional mode and to the shift configuration in the test shift mode. A clock multiplexing circuit (15a-c, 18) has inputs coupled to the data terminals (11a-c) and outputs coupled to clock inputs of the groups (12a-c).

Abstract: The invention relates to an electronic circuit including a sub-module assembly (2) connected to the rest of the circuit, the sub-module assembly including a secret sub-module (4) for performing a function, scan chains; a built-in self test circuit including a pattern generator (5) to apply input signals to the scan chains, and a signature register (6) to check output signals from the scan chains. In order to keep the sub-module secret, the scan chains are not connected to the rest of the circuit.