| 摘要 |
PURPOSE:To make intermission and resumption of DMA transfer possible by simple constitution by executing repeatedly the same microprogram that makes direct memory access (DMA) transfer of image data responding to an interrupt request signal. CONSTITUTION:When an interrupt request signal is generated asynchronously from an external equipment 16, this is detected by an interrupt I/F circuit 17, and conditional input signals are made low level until a processor 11 completes interrupt processing and outputs a DMA transfer starting signal again to DMAC 15 and the circuit 17. Under such a condition, DMAC 15 execute N steps of a microprogram, and transfers image data. In such a case, the microprogram of N-th step executes conditional jump as the conditional input signal is low level, and repeats jump to one's own address until the conditional input signal goes to high level. Thus, DMA transfer of image data can be easily intermitted by simple constitution, and at the same time, DMA transfer can be easily resumed responding to a DMA transfer resuming signal after completion of interrupt processing.
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