Lesson 048
Communicating with Peripherals
Buses · Registers · Memory-mapped I/O
1:00How the CPU uses buses, device controllers, and registers to talk to keyboards, disks, GPUs, and other peripherals — and why polling, interrupts, and DMA exist.
By the end, you can
- Explain why the CPU communicates with a device controller rather than the physical device.
- Describe the role of the address, data, and control lines on a bus.
- Identify which of the three controller registers the CPU reads vs writes, and when.
- Distinguish memory-mapped I/O from port-mapped I/O and state the instruction used for each.
- Trace the steps a CPU takes to send one byte via programmed I/O, including both polling loops.
- Explain why polling busy-waits waste CPU cycles and how interrupts eliminate that waste.
- Describe how DMA improves on interrupt-driven I/O for large block transfers.
- Explain why device register addresses must be treated as volatile and never cached.
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