Patent ID: 11927633
Assignee: TEXAS INSTRUMENTS INCORPORATED
Field: Measurement (Instruments)
Classification: CPC G | IPC G

Claim 15:
16. A method of testing a device under test, the device under test comprising a scan chain including a plurality of storage elements and an output buffer, the method comprising:
providing, in a scan in phase, a scan clock signal and a scan in signal to the device under test to load the storage elements of the scan chain, wherein a shadow shift register of the device under test is loaded responsive to the scan clock signal and a scan output of one of the storage elements of the scan chain;
providing, in a capture phase, a signature clock signal and a signature data signal to the device under test to load a signature register of the device under test, wherein a value of the shadow shift register is latched before the capture phase; and
providing, in a scan out phase, the scan clock signal to the device under test to unload the storage elements of the scan chain through the output buffer,
wherein the output buffer provides a high-impedance output responsive to the latched value of the shadow shift register being unequal to a value of the signature register, and
wherein the output buffer provides an output signal corresponding to values of the storage elements of the scan chain responsive to the latched value of the shadow shift register being equal to the value of the signature register.