Nec Corporation

Nippon Telegraph and Telephone Corporation

Iwatsu Electric Company Ltd.

Yasuhiro Sota

Masanobu Abe

Syohei Suzuki

Hironori Ohata

Tsutomu Irishima

Keiichi Nakayama

Conference telephone

A requester includes an output data register which retains a data piece to be output to a relay register of a crossbar, and two request registers which output a request corresponding to the data piece. The requester sets a next data piece in the output data register, and sets a corresponding request in the request register in response to a selection signal from the crossbar. The crossbar outputs a grant signal representing that output of a data piece output from the requester to an output port is permitted to the requester, and at the same time, switches selection between requests from the two request registers in accordance with a request selection register prepared in advance, and inputs the selected request to an arbiter.

Crossbar system with increased throughput

A DMA transfer device according to the present invention allows data to be transferred from non-consecutive addresses. A logical address controller checks if logical addresses of data transferred from an input/output bus are consecutive. If they are not consecutive, the logical address controller sends an address non-consecutive interrupt to an input/output controller. The input/output controller sets a physical address, corresponding to the logical address received from the input/output bus, into a physical address controller. The physical address controller checks if a page change has occurred in the physical address and, if it detects the page change, sends a page change interrupt to the input/output controller.

Data transfer apparatus performing DMA data transfer from non-consecutive addresses

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Tokyo, Japan

Yasuhiro Sota