What is the mode of information transmission between the blocks in microprocessor?

1 Answer

  • Anonymous
    1 month ago

    Data transfer between processor and i/o devices. Well generrally we classify them into the following modes.

    1. Polled mode

    2. Interrupt driven

    3. DMA

    In polling, the 8086 keeps reading and checking some status signal to find whether data is ready and reads it off the i/o port when the status signal is asserted. Polling loads the processor and it has to sit in a loop doing the reading, waiting for the data to arrive.

    In interrupt the status signal is suitably tied to one of the interrupts of 8086. When the I/O device interrupts, the processor reads the data from the port during the ISR (interrupt service routine). This is better but still the overheads can pile up if the amount of data to be read is large.

    DMA stands for Direct Memory Access. DMA is performed by a DMA controller. The DMA controller is programmed by the processor by specifying the i/o port address, target memory address and the no. of bytes to be transfered etc. Now the bus control is relinqueshed by the processor and the DMA controller runs the bus cycles and performs the transfer.

    Hope this is what you were looking for

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