INTRODUCTION TO MICROPEOCESSOR
MICROPROCESSOR BASICS
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Question
[CLICK ON ANY CHOICE TO KNOW THE RIGHT ANSWER]
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DMA controller to CPU
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CPU to IO device
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CPU to DMA controller
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IO device to DMA controller
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IO device to CPU
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Detailed explanation-1: -Explanation: The Controller uses the registers to store the starting address, word count and the status of the operation. When the R/W bit of the status register of the DMA controller is set to 1.
Detailed explanation-2: -The processor initiates the DMA controller by sending the memory addresses, number of blocks of data to be transferred and direction of data transfer.
Detailed explanation-3: -Initially, when any device has to send data between the device and the memory, the device has to send DMA request (DRQ) to DMA controller. The DMA controller sends Hold request (HRQ) to the CPU and waits for the CPU to assert the HLDA. Then the microprocessor tri-states all the data bus, address bus, and control bus.
Detailed explanation-4: -With DMA, the CPU first initiates the transfer, then it does other operations while the transfer is in progress, and it finally receives an interrupt from the DMA controller (DMAC) when the operation is done.