Clock stop and restart control to pipelined arithmetic processing units processing plurality of macroblock data in image frame per frame processing period

Abstract

A digital VLSI circuit is provided with functions in which the number of switching operations to supply electric power to each arithmetic operation unit is reduced in a restricted period of time while electric power supply is controlled for each arithmetic operation unit, so that low power consumption can be achieved in real pipe-line arithmetic operation. The VLSI circuit that performs each stage of the pipe-line arithmetic operation is comprised of a plurality of arithmetic operation units for carrying out arithmetic operations in synchronization with a clock signal, a detecting means for detecting completion of the stage in the arithmetic operation assigned to the arithmetic operation unit, and a clock signal supply control means for controlling supply/stop operation of the clock signal to each arithmetic operation unit, wherein the clock signal supply control means stops supplying the clock signal to a certain arithmetic operation unit when the detecting means detects the completion of the arithmetic operation assigned to the same, and restarts supplying the clock signal to all the arithmetic operation units for a next pipe-line arithmetic operation when the detecting means detects the completion of the arithmetic operations assigned to them.