Protecting Hidden Content In Integrated Circuits

摘要

Various integrated circuits protect hidden content e.g., embedded instruments, keys, data, etc.) using scan cell circuit(s). For example, a first scan cell circuit is connected to the hidden content, and a second scan cell circuit is connected to the first scan cell circuit forming all or part of a serial data path. The first scan cell circuit provides access to the hidden content whenever the first scan cell circuit is in a first specified state and prevents access whenever the first scan cell circuit is in a different state. The first scan cell circuit does not interrupt the serial data path when the first scan cell circuit is in the different state. The second scan cell circuit changes an operational characteristic of the first scan cell circuit whenever the second scan cell circuit is in a second specified state. In some cases, the second scan cell circuit can be eliminated.

主权项

1. An integrated circuit comprising:
one or more hidden content; a first scan cell circuit connected to at least one of the one or more hidden content; a second scan cell circuit connected to the first scan cell circuit; the first scan cell circuit and the second scan cell circuit form all or part of a serial data path; the first scan cell circuit provides access to the at least one of the one or more hidden content whenever the first scan cell circuit is in a first specified state and prevents access to the at least one of the one or more hidden content whenever the first scan cell circuit is in a different state than the first specified state; the first scan cell circuit does not interrupt the serial data path when the first scan cell circuit is in the different state; and the second scan cell circuit changes an operational characteristic of the first scan cell circuit whenever the second scan cell circuit is in a second specified state.