Serial Interfaces

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Serial Interfaces
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Bit serial bus

• New generation of busses
• Uses bit-serial, differential drive technology
• Uses on-line device drivers (Hot-plug technology)
• Automatically detects plugged in devices and
  configures the controlling software
• Two main tech USB and Firewire

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USB Universal Serial Bus
vdd,gnd

• 12 Mb/s serial bus
• Hot-plug tech (plug play)
• Supports up to 127 external
• devices
• Provides power
• USB 2.0 480 Mb/s serial bus

D, D-
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Bus topology

• Tiered star structure, up to tier 6

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USB devices

• HUB
• Serve to USB connectivity
• Can detect attach and detach
• Hub Controller Hub repeater
• Functions
• USB device that is able to transmit or receive
  data

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USB host

• Client
• Describes all the software entities that are
  responsible for USB devices
• USB System
• Translation between the client data and USB
  transaction on the interconnect
• Managing USB resources(bandwidth, power )
• USB Bus interface
• Handles interactions for the electrical protocol
  layer

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USB data flow
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Bus Protocol
data transfer
handshake

• Host controller initiates data transfer by
  generating token packet
• Data transferred
• Handshake packet for completion

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Attach and Remove of USB Devices
Host
Hub
upstream port
port
port
port
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Data flow types

• Control transfers
• configure device at attach time
• Bulk data transfers
• generate or consume large data. error detection
  and retries used ex) file Xfer
• Interrupt data transfers
• Small, limited latency transfer ex) event
  notification, echo from device
• Isochronous data transfers
• Continuous and irregular data. ex) voice

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Firewire

• 400 Mbps ( 3200Mbps for 1394b )
• Plug play
• Support 63 devices
• Provides power
• Comparison to USB
• USB is host-based(must be connected to computer),
  Firewire is peer to peer (two devices can be
  connected directly)

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Website

• http//www.usb.org
• http//www.apple.com/firewire