Amdahl Corporation

Dale F Merrick

Stephen S Si

Disclosed is a scan apparatus which provides an interface and control signals between a secondary computer and data locations in a host computer. The scan apparatus functions independently of the normal operation of the host computer. Scan-out is performed transparently to the operation of the host computer. The host computer is organized into a plurality of functional units. Each functional unit is constructed of circuits on semiconductor chips. The semiconductor chips are organized in blocks. In the present invention, each block within the host computer includes a multimode scan apparatus which controls the scan operations in connection with that block. The scan apparatus in each block is connected to the secondary computer by clock and scan lines. The scan apparatus on each block includes a multimode sequencer which is controlled by the secondary computer and independently of the operation of the host computer, executes the scan sequences for performing the scan operations associated with the block.

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Yamhill, OR, United States of America

Dale F Merrick