Abstract: A boundary scan tester is provided for testing logic devices. The boundary scan tester includes a boundary scan register, a data decompressor, a data compressor, and a derived boundary scan register. The boundary scan register registers the applied test vectors and test responses of a logic device, and the data decompressor is coupled to an input of the boundary scan register for decompressing the applied compressed test vectors. The data compressor is coupled to an output of the boundary scan register for compressing the test responses, and the derived boundary scan register is coupled to an input of the decompressor and an output of the compressor for storing and shifting in/out the compressed test vectors and test responses.

Abstract: An enhanced JTAG interface provides an additional clock output at any desired I/O port of a logic device during normal operation. The interface includes a boundary scan data cell associated with each I/O port that enables either input data to the I/O port in a normal mode or routes the boundary scan input data during a JTAG operation. A control cell is associated with each data cell for selectively enabling either a normal mode or a JTAG mode of the boundary scan cell. A set of JTAG instructions enable/disable JTAG operation and select JTAG functions. The boundary scan data cell is modified to incorporate a multiplexing arrangement to selectively route the JTAG clock to the I/O port when required. The control cell is modified to selectively enable/disable the routing of the JTAG clock in the boundary scan data cell.

Abstract: An improved 2-bit boundary scan test circuit capable of applying boundary scan test vectors to the input of the core logic of a circuit, using a multiplexer for selectively coupling the output of a boundary scan register to the input of a boundary scan register or to the input of the core logic, and a selection circuit for controlling the multiplexer to enable the coupling when test vectors are required to be applied to the core.

Abstract: A boundary scan tester is provided for testing logic devices. The boundary scan tester includes a boundary scan register, a data decompressor, a data compressor, and a derived boundary scan register. The boundary scan register registers the applied test vectors and test responses of a logic device, and the data decompressor is coupled to an input of the boundary scan register for decompressing the applied compressed test vectors. The data compressor is coupled to an output of the boundary scan register for compressing the test responses, and the derived boundary scan register is coupled to an input of the decompressor and an output of the compressor for storing and shifting in/out the compressed test vectors and test responses.

Abstract: An enhanced JTAG interface provides an additional clock output at any desired I/O port of a logic device during normal operation. The interface includes a boundary scan data cell associated with each I/O port that enables either input data to the I/O port in a normal mode or routes the boundary scan input data during a JTAG operation. A control cell is associated with each data cell for selectively enabling either a normal mode or a JTAG mode of the boundary scan cell. A set of JTAG instructions enable/disable JTAG operation and select JTAG functions. The boundary scan data cell is modified to incorporate a multiplexing arrangement to selectively route the JTAG clock to the I/O port when required. The control cell is modified to selectively enable/disable the routing of the JTAG clock in the boundary scan data cell. The JTAG instruction set is enhanced to incorporate instructions to select the desired I/O port and to enable the routing.

Abstract: An improved 2-bit boundary scan test circuit capable of applying boundary scan test vectors to the input of the core logic of a circuit, using a multiplexer for selectively coupling the output of a boundary scan register to the input of a boundary scan register or to the input of the core logic, and a selection circuit for controlling the multiplexer to enable the coupling when test vectors are required to be applied to the core.