Graphics engine command FIFO for programming multiple registers using a mapping index with register offsets

Abstract

A host writes graphics commands and data to programmable registers through a command FIFO that is read by a graphics controller or BitBlt engine. Rather than write an address and a data value for each register programmed, the host writes one address, one index, and several data values. The address points to an index register. The index is a mapping index word with several multi-bit mapping fields. Each multi-bit mapping field in the index identifies a register to be programmed with one of the data values. Since N bits are used for each mapping field, the mapping field can select one register in a bank of 2N−1 registers. The registers in the bank can be programmed in any order, and registers can be skipped. Since only one index is stored in the command FIFO for programming several registers, less memory space and fewer bus cycles are required.

Description

BACKGROUND OF INVENTION[0001]This invention relates to graphics systems, and more particularly to addressing of programmable registers.[0002]Personal computers (PCs) and other computer systems have a variety of controller integrated circuits (ICs) or chips that control subsystems such as for graphics, disks, and general system logic. Such controller chips are usually programmable. For example, the graphics controller can be programmed with the display resolution, such as the number of pixels in a horizontal line, or the number of lines on a screen. Memory-controller chips can be programmed with numbers of clock cycles for memory accesses, so that the timing signals generated by the controller chip can be adjusted for faster memory chips or faster bus clocks.[0003]Advanced graphics systems often employ specialized engines, such as a bit-block-transfer BitBlt engine. Graphics data and commands can be written to a command first-in-first-out (FIFO) by a host processor, allowing the BitB...

AI Technical Summary

Problems solved by technology

Thus the number of I / O addresses available to a peripheral controller chips is often limited.

Since registers A3, A5 are not being written, a burst access to write the registers is not possible.

When even one register in the burst sequence is not written, then burst access may not be possible.

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