| 摘要 |
PROBLEM TO BE SOLVED: To prevent the load of internal processing from increasing, even if the polling frequency is increased in a terminal device, that conducts data transmission with polling from a host computer as a turning point. SOLUTION: The communication terminal, provided with a DMA controller, is provided with a means for performing comparison to check whether data received by a receiving circuit are a polling signal or received data and also a discrimination means for deciding the presence/absence of data to be transferred in the case of the polling signal, and completes processing without updating an address register value or a transfer counter value of the DMA controller, when the received data are a polling signal and also when there are no data to be transferred. Communication processing is possible, without causing increase in load so much in the terminal device even though a polling frequency from the host computer is increased, not by performing CPU interrupt to the entire polling but by performing CPU interrupt, after deciding the existence/ nonexistence of transmission data in the communication terminal in this way.
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