Data transfer control device using direct memory access

Abstract

When DMA transfer for a DMA transfer area is completed, DMA transfer for the next area may be continuously executed or stopped. In addition to this, if there is a need to urgently stop DMA transfer being executed, DMA transfer can be immediately stopped without waiting for the end of DMA transfer currently executed. For continuous DMA transfer for a plurality of DMA transfer areas, the device may be provided with an authorization bit to authorize DMA transfer operation and a next area authorization bit to authorize DMA transfer for the next area and the contents in the next area authorization bit are set to the DMA authorization bit when the terminal counter which counts the number of DMA transfer data reaches the predetermined value due to decrement. Depending on the contents in the DMA authorization bit, DMA transfer may be continued or stopped when the next DMA transfer request is generated. In addition, DMA transfer may be stopped in emergency by directly setting the applicable value at the DMA authorization bit.