- 2075 Chaitra · 6 marks
USB standards and data transfer mechanisms
Short answer
USB standards span from USB 1.1 to USB4 v2.0 (80 Gbps) with Type-C. Transfer mechanisms: control for enumeration, bulk for large data (e.g., pen drive), interrupt for keyboards/mice with guaranteed latency, and isochronous for real-time audio/video (e.g., webcam) without retry.
Describe up to date USB standards. Differentiate different USB data transfer mechanisms with suitable example of each.
USB standards (up to date)
| Standard | Year | Name / speed | Notes |
|---|---|---|---|
| USB 1.0 / 1.1 | 1996 / 1998 | Low 1.5 Mbps, Full 12 Mbps | First widespread version |
| USB 2.0 | 2000 | High speed 480 Mbps | Backward compatible, OTG |
| USB 3.0 / 3.1 Gen 1 / 3.2 Gen 1 | 2008 | SuperSpeed 5 Gbps | Extra differential pairs, full duplex, 900 mA |
| USB 3.1 Gen 2 / 3.2 Gen 2 | 2013 | SuperSpeed+ 10 Gbps | 128b/132b encoding |
| USB 3.2 Gen 2x2 | 2017 | 20 Gbps | Two lanes via Type-C |
| USB4 (v1) | 2019 | 40 Gbps | Based on Thunderbolt 3, tunnels PCIe and DisplayPort |
| USB4 v2.0 | 2022 | 80 Gbps (120 Gbps asymmetric) | Type-C, up to 240 W power (USB PD 3.1) |
| Connector: Type-A, Type-B, Mini, Micro, and reversible Type-C. |
USB data transfer mechanisms
| Type | Use | Characteristics | Example |
|---|---|---|---|
| Control | Configuration and commands | Reliable, reserved bandwidth, three stages | Enumeration of any device |
| Bulk | Large non-time-critical data | Reliable (retry), uses free bandwidth, no latency guarantee | Pen drive file copy, printer |
| Interrupt | Small data at guaranteed intervals | Host polls, reliable, bounded latency | Keyboard, mouse |
| Isochronous | Real-time streaming | Guaranteed bandwidth/latency, no retry | USB microphone, webcam |
✓ Answer checked by Claude Sonnet 5.5
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