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USB
SERIAL BUS STANDARD TO INTERFACE DEVICES
Allow devices to be connected with single std. scoket
Allow plug n play i.e connecting and disconnecting without rebooting computer
i.e hot swapping
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2. Low power consumption
No need of external power supply
Allow devices to be used w/o drivers installed
Can connect mouse, k/b,joystick, cameras,printers,scanners..
Designed by USB_IF(incorporating Forum)
V can install and remove devices without opening case

3. Usb is better than RS232 Easy installation Fast transfer rate
Simple cabling
Multiple device connection

4. versions Low speed 1.5mb/s used for k/b, mouse, joystick
Full speed 12mb/s USB 2.0 FCFS rule for many devices
Hi Speed of 480mb/s
Super Speed 4.8Gb/s

5. Features Host Multiple devices 127 Cable length 5 to 30m
Transfer rate 12 mb to480mb/s
Ease of installation
Hot swappable plug and unplug anytime
Hot pluggability BIOS feature allow to plug n play

6. Power saving
Support wide range of devices
Hub architecture

7. Connectors & cables A upstream towards computer
B downstream to individual devices
Max length of cable is 5m
26 ns delay is maximum
Contains 4 wires
VCC red +5v
D- white Data-
D+ green Data+
GND Black Ground

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Usb process
Host queries all devices and assigns address to each is called enumeration
Each device transfer different data
1)Interrupt little data mouse,k/b
2)Bulk data in one big pkt printer 64 byte
3)Isochronous streaming devices example speakers
USB divides BW into frames first for isochronous nd remaining for other bulk and interrupt
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