Patent ID: 6272657
Filing Date: 2001-08-07
Classification: G01R

Abstract:
A test circuit adapted for testing input and output circuitry of an integrated circuit (IC), the IC comprising input-only lines, output-only lines and bidirectional line sets, each bidirectional line set comprising an input line, an output line and an output enable line, the test circuit comprising:a plurality of first coupling circuits, each being associated with one of the input-only lines, each first coupling circuit having first and second inputs and an output, the first input of each first coupling circuit being connected to its associated input-only line;a plurality of first selector circuits, each being associated with one of the output-only lines, each first selector circuit having first and second inputs, an output and a control input adapted to selectively couple the output to the first input or the second input, the first input of each first selector circuit being connected to its associated output-only line;a plurality of second coupling circuits, each being associated with one of the bidirectional line sets, each second coupling circuit having first and second inputs and an output, the first input of each second coupling circuit being connected to the input line of its associated bidirectional line set; anda plurality of second selector circuits, each being associated with one of the bidirectional line sets, each second selector circuit having first and second inputs, an output and a control input adapted to selectively couple the output to the first input or the second input, the first input of each second selector circuit being connected to the output line of its associated bidirectional line set; anda test select signal line coupled to the control input of each of the first and second selector circuits;all of the coupling and selector circuits arranged to form a single test chain, wherein a beginning circuit of the test chain is one of the first coupling circuits, wherein the outputs of the first and second coupling circuits each is coupled to the second input of one of the coupling circuits or one of the selector circuits, wherein the second inputs of the first and second selector circuits each is coupled to the second input of one of the coupling circuits or one of the selector circuits, and wherein an ending circuit of the test chain is one of the first selector circuits.