Method and apparatus for implementing enhanced LBIST diagnostics of intermittent failures

A method for implementing enhanced Logic Built in Self Test (LBIST) diagnostics of intermittent failures in a plurality of sequential channels under test, said method comprising the steps of:

• providing a plurality of first multiplexers;
• a respective one of said plurality of first multiplexers coupled between adjacent sequential channels;
• applying a first control signal to said first multiplexers for selectively configuring said sequential channels in a common scan path to receive a first data input in a first scan mode and each said sequential channels in a separate scan path to receive a second data input in a second scan mode;
• providing a second multiplexer, coupled between a test data output of a last sequential channel and said first data input of a first sequential channel;
• applying a recirculated control signal to said second multiplexer for selectively applying one of said test data output of said last sequential channel to said first data input of a first sequential channel and an external test data input;
• providing a first multiple input signature register (MISR) having multiple MISR inputs coupled to a respective one of said plurality of sequential channels under test;
• providing a blocker function coupled between said first multiple input signature register and said plurality of sequential channels under test;
• applying said recirculated control signal to said blocker function for blocking all MISR inputs except for a single MISR input receiving said test data output of said last sequential channel;
• and
• providing a second MISR shadow register coupled to said first multiple input signature register.