Serial Interfaces Bit serial bus n New generation
Serial Interfaces
Bit serial bus n New generation of busses n n 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
USB : Universal Serial Bus vdd, gnd n 12 Mb/s serial bus Hot-plug tech (plug & play) Supports up to 127 external devices Provides power n USB 2. 0 : 480 Mb/s serial bus n n n D+, D-
Bus topology n Tiered star structure, up to tier 6
USB devices n HUB n n Serve to USB connectivity Can detect attach and detach Hub Controller + Hub repeater Functions n USB device that is able to transmit or receive data
USB host n Client n n USB System n n n Describes all the software entities that are responsible for USB devices Translation between the client data and USB transaction on the interconnect Managing USB resources(bandwidth, power …) USB Bus interface n Handles interactions for the electrical protocol layer
USB data flow
Bus Protocol data transfer token n • Type of transaction • Direction of trans. handshake • USBdevice address Host controller initiates data transfer by generating ‘token packet’ n Data transferred n Handshake packet for completion
Attach and Remove of USB Devices • Enable port • allocate Remove USB address upstream port indicato disable r r Hub port Host device
Data flow types n Control transfers n n Bulk data transfers n n generate or consume large data. error detection and retries used ex) file Xfer Interrupt data transfers n n configure device at attach time Small, limited latency transfer ex) event notification, echo from device Isochronous data transfers n Continuous and irregular data. ex) voice
Firewire n n n 400 Mbps ( 3200 Mbps for 1394 b ) Plug & play Support 63 devices Provides power Comparison to USB n USB is host-based(must be connected to computer), Firewire is peer to peer (two devices can be connected directly)
Website n http: //www. usb. org n http: //www. apple. com/firewire
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