| 摘要 |
PURPOSE:To attain ROM operation of a digital filter having lots of tap numbers by providing an accumulator adding outputs at each ROM split into plural numbers and adding the outputs to decrease the capacity of the ROM. CONSTITUTION:The ROM is divided into three, x1-x6 among outputs x1-x18 from each delay element SR are used as addresses of a ROM4A, x7-x12 are addresses used for a ROM4B, and x13-x18 are addresses used for a ROM4C. Moreover, accumulators 8A-8C comprising a parallel adder ADD, a register R and a shifter S are provided to each divided ROM, outputs yA-yC of each accumulator are added by an adder 9 and an output (y) is obtained. Thus, 64 words are enough for the capacity of the ROM4A and this is applied also to the other two ROMs, then the number of words are 192 words in total, thereby decreasing the capacity of ROM. |
