W10_18_IO4_DMA - c) The DMA sends an interrupt signal to...

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18 I/O and Peripherals Part 4: DMA CSC 230 1
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What is a DMA = Direct Memory Access ± Interrupts frees CPU while waiting for I/O ± Yet CPU remains in charge of ALL I/O transfers ± What abouttransfers disk Î memory in large blocks? DMA Transfer from Disk to Memory Bypasses the CPU after the initial setup) (after the initial setup) With DMA 2
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DMA processs and controls 1) Processor initiates the data transfer by sending information to the DMA controller: a) which I/O device b) how many bytes to transfer to which location 2) DMA controls the data transfer between the device and memory while the processor is free for other work a) There is some form of handshaking between the DMA and the device to coordinate the transfer. b) Use of buses by processor and DMA controller may be interleaved ) he MA sends an interrupt signal to the CPU when
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Unformatted text preview: c) The DMA sends an interrupt signal to the CPU when the data transfer is complete he DMA device is really a simple special purpose 3 The DMA device is really a simple special purpose processor DMA Protocol Issue 1: who uses and controls the bus? emory Processor Main bus is memory System bus common! Keyboard Disk/DMA controller Printer DMA controller Interface Network Disk Disk 4 New strategy: cycle stealing, bus mastering DMA Protocol Issue 2: extra bus, extra hardware? address data memory Processor input DMA terrupt output interrupt New solution also equires dual port 5 optional connection requires dual port memory DMA Flowchart for a Disk Transfer 6 Computer Architecture and Organization by M. Murdocca and V. Heuring 2007 M. Murdocca and V. Heuring...
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W10_18_IO4_DMA - c) The DMA sends an interrupt signal to...

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