Boots – shoes – and leggings
Patent
1991-12-30
1994-11-22
Gossage, Glenn
Boots, shoes, and leggings
395425, 364DIG1, G06F 1328
Patent
active
053676394
ABSTRACT:
An apparatus and method for performing direct memory access (DMA) to input/output (I/O) devices are described. In order to overcome storage limitations of a DMA controller, channel control blocks (CCBs) are stored in external memory. The DMA controller is programmed to reference a particular address of the external memory when a predetermined bit, referred to as a chain bit, in a current channel control block is set. The DMA controller will then perform a memory read operation on that area of memory and store a retrieved channel control block at a location previously utilized by an earlier channel control block. This process will continue until the chain bit is reset, at which time a DMA operation is complete. Dynamic chaining is easily accommodated whereby channel control blocks can be dynamically changed during the DMA access to provide a flexible I/O system. The apparatus and method may be used to implement dynamic chaining without incurring race conditions. A wait bit is provided in each channel control block and, when this bit is set, the DMA controller will suspend operations thereby providing an opportunity for updating a chain of CCBs without incurring errors due to race conditions. Once the chain has been modified, the wait bit is reset and processing safely continues.
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patent: 4837677 (1989-06-01), Burrus, Jr. et al.
patent: 4930065 (1990-05-01), McLagan et al.
patent: 5251312 (1993-10-01), Sodos
Gossage Glenn
Sun Microsystems Inc.
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