I/O Interfaces & Buses

Among USB transfer types, what is characteristic of isochronous transfers?

  1. AThey retry on any error to guarantee correct delivery; used for file transfers
  2. BThey reserve bandwidth and send at fixed intervals but do not retry on error; used for audio and video
  3. CThey are used only when configuring a device
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Answer: B. They reserve bandwidth and send at fixed intervals but do not retry on error; used for audio and video

USB has control transfers for configuration, interrupt transfers for devices such as mice, bulk transfers for reliably moving large data and isochronous transfers for on-time delivery. In audio and video, data that arrives late is useless, so isochronous transfers reserve bandwidth, send at fixed intervals and do not resend on error. Smooth playback is prioritized over losing a little data.

  • A. That describes bulk transfers.
  • B. Correct. It suits uses where a small gap beats a delay.
  • C. Configuration uses control transfers.
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More I/O Interfaces & Buses questions

  1. Which describes hot plugging, supported by USB and some PCI Express setups?
  2. Which bus from Arm's AMBA specifications is widely used to connect blocks such as CPUs, memory controllers and peripherals inside an SoC?
  3. What is a characteristic of the AXI bus?
  4. In the VALID/READY handshake used on each AXI channel, when is data transferred?
  5. What is the advantage of burst transfers in AXI?