The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Mar. 26, 2002
Filed:
Feb. 03, 1999
Emrys John Williams, Sunnyvale, CA (US);
Andrew Crosland, Haddenham, GB;
Sun Microsystems, Inc., Palo Alto, CA (US);
Abstract
A direct memory access (DMA) controller is provided for a computer system having a processor and a command buffer. The command buffer can be defined, for example, as a ring buffer in the main processor memory and can be directly accessible by the processor, for example over a bus. The DMA controller provides a head register and a tail register operable to hold a head pointer and a tail pointer for addressing the head and tail, respectively, of a sequence of direct memory access commands in the command buffer. The processor is able to store DMA commands in the command buffer. Subsequently, the DMA controller is able to access those DMA commands using the DMA tail pointer held locally in the DMA controller. The DMA controller is operable to compare the head and tail pointers, and to respond to non-equivalence thereof to use the tail pointer value to access direct memory access commands from the command buffer. The DMA controller is responsible for updating the tail pointer in the DMA controller in association with reading of a direct memory access command from a location in the command buffer. The processor is responsible for updating the head pointer in the DMA controller in association with the storing of DMA commands in the command buffer.