Patent ID: 7786739

Claim:
A device for testing the connections to a differential receiver, wherein the differential receiver includes a first positive input connected to a first input/output pad, a second negative input connected to a second input/output pad, and an output, comprising: at least one test receiver coupled to a corresponding one of the first input/output pad and the second input/output pad, wherein the test receiver includes a single-ended comparator with an output coupled to an input of a data storage register, and wherein the test receiver includes an output coupled to a JTAG capture register, wherein at least one capture/update register is coupled to the output of the differential receiver, and wherein the JTAG capture register is coupled to the capture/update register; and a capacitor coupled in series between the input/output pad and the input to the test receiver in a manner that protects the input of the test receiver from DC voltages coupled to the differential receiver via the input of the differential receiver, and wherein the at least one test receiver includes a high-pass filter arrangement that generates data of a first type if the input/output pad coupled to the test receiver has a proper DC-coupled connection and data of a second type if the input/output pad coupled to the test receiver has an improper connection.