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 confi
gures the controlling software Two main tech : USB and Firewire
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USB : Universal Serial Bus
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
vdd,gnd
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
Host controller initiates data transfer by generating ‘token packet’
Data transferred
Handshake packet for completion
handshake
data transfer
token•Type of transaction•Direction of trans.•USBdevice address
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Attach and Remove of USB Devices
Host
Hubport
port
port
upstream port
device
•Enable port•allocate USB address
indicator
disable
Remove
indicator
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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 fr
om 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