计算机专业毕业论文外文翻译.docx

外文资料
Data Transfer Techniques
The actual transfer of data between the puter and external and external devices monly carried out using three different techniques:
(1)ling;(2)errupters; (3) emory access; These techniques can be used individually or bination..
Polling
Polling routines are used for programmed input/output number of peripheral devices attached to the outer are continuously polled at specified time intervals to determine the device wishes to input data to the ssor. Similarly, for the transfer of data to an output device,the state of its buffer is checked to determine if it is empty and ready to receive the data. A soft program is required to check the state of the peripheral devices. Hardware flaga are used to indacate the send or receive condition of the peripheral. If a device is ready to transfer the data, then an appropriate software routine is used to service that particular device so that data transfer can take place .It is necessary to ensure that none of the data from any of the peripherals are lost while the polling routines or any the peripheral devices servicing routines are being executed. The probability of loseing data is very small since most perpheral are slow deices. Other techniques, such as direct memory access(DMA) , can be used to achieve high-speed data transfer from a given peripheral.
Polled input/output is very simple mon met