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LSSD Testable Derived B Clock Design Disclosure Number: IPCOM000039066D
Original Publication Date: 1987-Apr-01
Included in the Prior Art Database: 2005-Feb-01

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Hanna, SD Williams, TW [+details]


A circuit design process is described which eliminates the need to bring derived B clocks in an LSSD design to an I/O pin to guarantee that all clocking faults in the B clock structure are testable. As compared to known LSI-structured designs, this can free one or more I/O pins for other purposes. The circuit implementation, as shown, makes the derived B clock testable by using it (properly gated by Clock Isolation pin(s)) to clock an L2* SRL system clock port or an L1 system port. Since the system clocks for L2* SRLs and L1 latches are testable, the B clock becomes testable without the use of a valuable I/O pin. This configuration does not need to be separate from the system design.