We address access control of reconfigurable scan networks, like IEEE Std. 1687 networks. We propose an on-chip test block to perform: (1) test for faulty scan-chains, (2) localization of faulty scan-chains and (3) repair by excluding faulty scan-chains, and an access control block to (1) control so scan-chains (instruments) are only accessed in allowed combinations, (2) detection of access attempts to instrument in not allowed combinations, and (3) monitoring how theses attempts are made. The key features are two-fold. First, in respect to operation and maintenance. If the physical implementation of an IEEE Std. 1687 network changes due to faults, the instrument connectivity language (ICL) and procedural description language (PDL) need to be updated. To avoid keeping track and updating ICL and PDL for each individual integrated circuit (IC), proposed test block, placed at each IC, makes adjustments of PDL according to the faults of the particular IC. Second, a centralized access control block with key information about the network to detect and handle unauthorized access.
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