Serial Interfaces

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

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-

Bus topology

Tiered star structure, up to tier 6

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

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

USB data flow

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

Attach and Remove of USB Devices

Host

Hubport

port

port

upstream port

device

•Enable port•allocate USB address

indicator

disable

Remove

indicator

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

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)

Website http://www.usb.org

http://www.apple.com/firewire