29. Overview of DMA and Interrupt Driven I/O
The chapter addresses the concepts and mechanisms of Direct Memory Access (DMA) and its differences from traditional interrupt-driven I/O. It discusses how DMA allows for data transfer directly between peripherals and memory, reducing CPU involvement and improving efficiency. Various transfer modes such as burst transfer and cycle stealing are explained, showcasing the flexibility and challenges of DMA operations.
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What we have learnt
- DMA transfers data directly between memory and peripherals without CPU intervention.
- The burst transfer mode sends all data at once, whereas cycle stealing allows for intermittent CPU access.
- Interrupt breakpoints in DMA depend on the current execution context, affecting how efficiently the processor can continue its tasks.
Key Concepts
- -- Direct Memory Access (DMA)
- A method for transferring data between memory and peripherals without requiring continuous CPU involvement.
- -- Burst Transfer Mode
- A DMA mode where the entire block of data is transferred in one go, temporarily suspending CPU operations.
- -- Cycle Stealing Mode
- A DMA mode that allows the CPU to access the bus intermittently, enabling both DMA transfers and CPU operations.
- -- Interrupt
- A signal that prompts the processor to suspend its current task and execute specific instructions in response.
- -- Context Switching
- The process of storing and restoring the state of a CPU so that multiple processes can share the CPU resources.
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