Cisco Technology, Inc.

Chandrasekhar Thyamagondlu Srinivasaiah

Udupi Harisharan

Chidambaram Ramaswamy

An apparatus and a method for testing Alternating Current (AC) coupled interconnects of a circuit using boundary scan methodology are disclosed. A Boundary Scan Cell (BSC) of a transmitting Integrated Circuit (IC) generates an AC signal based on a value of the BSC of the transmitting IC and a reference clock. A Sync Pulse cell at the receiving IC generates a sync pulse signal to the BSC of the receiving IC. The BSC of the receiving IC captures a default phase of the AC signal in relation to the sync pulse signal and also captures a phase of a source of input signal. The BSC of the receiving IC then compares the phase of a source of input signal with the phase of said AC signal in relation to the phase captured at the snyc pulse signal and sends out an output signal based on the comparison.

Boundary scan cell for testing AC coupled line using phase modulation technique

A boundary scan cell of a driving integrated circuit transmits an AC signal to a boundary scan cell of a receiving integrated circuit. Both integrated circuits are AC coupled by a capacitor. The transmitted AC signal has a frequency lower than a cut-off frequency of the capacitor. A comparator coupled to the AC signal at the driving IC and the signal at the receiving IC compares both signals and determines whether the capacitor is short-circuited.

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San Jose, CA, United States of America

Chandrasekhar Thyamagondlu Srinivasaiah