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:
Sep. 16, 1997
Filed:
Jun. 22, 1995
Ali Noorbakhsh, Danville, CA (US);
Cirrus Logic, Inc., Fremont, CA (US);
Abstract
A method and apparatus for improving performance of bit block transfers in display controllers during clipping functions without significantly increasing gate count. In a clipping function, particularly when transferring a portion of a monochrome bit map and color expanding same or in pattern copying, a source start address may not lie on a byte boundary. In order to avoid using time consuming shift left operations in software, the source start address may be adjusted in hardware to an earlier byte boundary. Upon writing data to a destination address, a hardware byte mask may be employed to prevent writing of the additional data retrieved due to the adjustment of the source start address. The source start address and byte mask hardware may be implemented in hardware using bit block transfer engine components and a small amount of additional hardware. The remainder of the clipping functions may remain in software, for example in a display device driver. By eliminating the shift left operations from the software portion of the clipping function, overall system performance is enhanced.