05032783 is referenced by 44 patents and cites 27 patents.

A test circuit for a logic device having ports. The test circuit includes a serial scan path for serially transferring externally generated test vectors from a serial test input to a serial test output. A storing circuit stores a data bit and has a node at which the data bit is stored. A first interface circuit interfaces the node with a first one of the ports for synchronous transfer of data from the logic device to the node. A second interface circuit interfaces the node with the serial scan path to tranbsfer data from the serial scan path to the node. A coupling circuit connects the storing circuit to a second of the ports to transfer a logic level responsive to the data bit to the logic device during test. Also the coupling circuit temporarily couples the data bit from the node to the serial scan path also during test. A third interface circuit is provided for an asynchronous input of data from the logic device to the coupling circuit except during test wherein the asynchronous input is isolated from the coupling circuit. A control circuit controls the third interface and the coupling circuit during test in response to an external test enable signal. In this way, the second interface is operable during test to store data in the storing circuit for input to the logic device, and the first interface transfers test results from the logic device to the storing circuit for extraction through the serial scan path.

Title
Test circuit and scan tested logic device with isolated data lines during testing
Application Number
790598
Publication Number
5032783
Application Date
July 10, 1989
Publication Date
July 16, 1991
Inventor
Theo J Powell
Dallas
TX, US
Yin Chao Hwang
Sugar Land
TX, US
Agent
James F Hollander
James T Comfort
Melvin Sharp
Assignee
Texas Instruments Incorporated
TX, US
IPC
G06F 11/00
G01R 31/28
View Original Source