| 摘要 |
Verification testing of modules packaged within an integrated circuit are conducted utilizing I/O ports of the integrated circuit for inputting or outputting incoming and outgoing signals, with three sets of externally controlled, tri-state buffers provided for each module. A first set selectively connects predetermined I/O contacts of each module interconnected to contacts of other modules, a second set selectively connects predetermined I/O contacts of each module to the I/O ports and a common test bus, and a third set applies the last logic state on each I/O contact before isolation by a buffer from the first set. Whenever a module is selected for testing, the current value that appears on each I/O contact that is connected to other modules is stored in its corresponding bus holder, so as to essentially prevent DC leakage currents.
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