1.      Overview of Bus Architectures

-          Firewire

-          USB

-          I2C

-          CAN

-          PCI

-          AGP

-          Fast Ethernet

-          Link16

-          ETC


2.      Comparison


3.      Terminology


4.      Papers & Discussion




Comparison of different Bus standards











One device/total








100, 200, 400




















3-5m /30m








0.1, 0.4, 3.4











0.063, 0.125, 0.8, 1.250








40m, 10m





1060 (132MBps)










2112 (264MBps)









4224 (528MBps)


8000 (1GBps)


16000 (2GBps)

Fast Ethernet






















1(real: 720k)






0.1-10m, 100m



















50m/115m (in/out)




1. Firewire(IEEE1394/i.Link/HPSB)



A high-speed serial bus that allows for the connection of up to 63 devices (16 - daisy chained) with cable length up to about 4.5 m (14 feet) for a total of 72m.  FireWire supports hot swapping, multiple speeds on the same bus and bi-directional isochronous data transfer, which guarantees bandwidth for multimedia operations. Hot-pluggable, plug&play bus. Since the power line is a part of the cable, power can be supplied directly to the low-power devices (mice, keyboard, etc.).



FireWire was invented in the mid-1990s by Apple Computer Inc and developed with Texas Instruments. It was originally developed to replace fast but complex SCSI.  Later, it was adopted as a standard, IEEE 1394. Sony Corp. and other firms call it iLink. The first commercial products implementing Firewire technology were Sony's DCR-VX700 and DCR-VX1000 digital video camcorders, introduced in 1995. Nowadays, growing variety of electronic products rely on the Firewire technology.



Any device that deals with lots of data is an ideal candidate for a FireWire connection. Eg) Computers, digital video camcorders, high-end digital cameras, TV sets, speakers, scanners, hard drives(Portable FireWire minidrives up to 60 GB)., optical burners, iPod music player(5GB HD)



http://www.mips.com/products/s2p8.html  0.12 - 0.37 mW/MHz at 1.2V (Core Only) Core Size: 0.4 - 1.9 mm









2. USB(Universal Serial Bus)



USB can support isochronous data transfer mode, but the bandwidth will be much lower than IEEE 1394 Firewire. In theory, a USB interface can support up to 127 individual USB peripherals at one time. The practical maximum number of devices is less since some of them reserve USB bandwidth. Additional PCI-based USB cards provide an independent USB bus so that even more peripheral devices can be connected. 
Devices are plugged directly into a four-pin socket on the PC or into a multi-port hub that plugs into the PC or into a device that also functions as a hub for other devices.

For practical connection of multiple devices to the host (root), special hubs are required.  Hubs notify the host when nodes (devices) attach or detach from the hub to provide the real-time reconfiguration of the system and device identification.  Hubs can have up to seven connectors to nodes or other hubs.  They could be self-powered or powered by the host.

The USB bus distributes 0.5 amps (500 milliamps) of power through each port. Port switching hubs isolate all ports from each other so that one shorted device will not bring down the others.




USB was originally developed in 1995, and USB ports began to appear on PCs in 1997.

The goal of USB was to define an external expansion bus, which makes adding peripherals to a PC easy, and low cost. On September 5th 2001, the USB Implementers Forum announced USB On-The-Go (OTG). USB OTG is a new supplement to the USB 2.0 specification (core team: Compaq, HP, Intel, Lucent, Microsoft, NEC and Philip). It augments the capability of existing mobile devices and USB peripherals by giving them a limited host capability for connection to other USB peripherals. USB has traditionally consisted of a host-peripheral topology where the PC was the host and the peripheral was a relatively dumb device. New features were needed to upgrade standard USB technology for mobile devices. These new features include:

USB OTG allows connection to many of the standard USB products that have shipped to date. Over 900 million USB enabled PCs and peripherals have been shipped, and connection to these products is the primary reason USB OTG is being rapidly adopted.




USB 1.1 system mainly supports low-speed peripherals such as the keyboard, mouse, joystick, scanner, printer and telephony devices. It also supports MPEG-1 and MPEG-2 digital video. 


Role of Host PC software: The system software will detect sub-optimal configurations (i.e. a USB 2.0 peripheral attached to a USB 1.1 hub) and will alert the user and recommend a better configuration for attaching the peripherals.


Spec & Reference




Universal Serial Bus Revision 2.0 specification





3. I2C (Inter-Integrated Circuit)


It is a two-wire serial bus, inheriting simple operation.  I2C is a multi-master bus, which means that multiple chips can be connected to the same bus and each one can act as a master by initiating a data transfer.



Philips was the inventor of the Inter-IC or IC-bus in the early 1980s, and it is now firmly established as the worldwide de-facto solution for embedded applications.



It is used extensively in a variety of microcontroller-based professional, consumer and telecommunications applications as a control, diagnostic and power management bus.

video devices such as computer monitors, televisions and VCRs.


Spec & Reference






4. CAN(Controller Area Network)



CAN is a serial network that was originally designed for the automotive industry, but has also become a popular bus in industrial automation as well as other applications. The CAN bus is primarily used in embedded systems, and as its name implies, is the network established among microcontrollers. It is a two-wire, half duplex, high-speed network system and is well suited for high speed applications using short messages. Its robustness, reliability and the large following from the semiconductor industry are some of the benefits with CAN.

CAN can theoretically link up to 2032 devices (assuming one node with one identifier) on a single network. However, due to the practical limitation of the hardware (transceivers), it can only link up to110 nodes (with 82C250, Philips) on a single network. It offers high-speed communication rate up to 1 Mbits/sec thus allows real-time control. In addition, the error confinement and the error detection feature make it more reliable in noise critical environment.


The ZIMO CAN-Bus is probably the most powerful and reliable data link used in model railroad control today. It works as a Local Area Network (LAN) with multi-master capability - there is no time-consuming polling by a central device. It uses CSMA/CD+AMP (Carrier Sense Multiple Access/Collision Detection with Arbitration on Message Priority).

The message label ID in the arbitration field is used to determine whether the data is relavant, and also to represent the priority of the message.  The ID is 11bit in 2.0A, 29bit in 2.0B.  (2032 or 500million unique Ids!)

It is highly fault tolerant, with powerful error detection and handling designed in.



CAN was first developed by Robert Bosch GmbH, Germany in 1986 when they were requested to develop a communication system between three ECUs (electronic control units) in vehicles by Mercedes. They found that an UART is no longer suitable in this situation because it is used in point-to-point communication. The need for a multi-master communication system became imperative. The first CAN silicon was then fabricated in 1987 by Intel.



Originally, used for cars.

self propelled wheel chair, dispensing system,



Spec & Reference






5. PCI(Peripheral Component Interconnect)






PCI (Peripheral Component Interconnect) remains a strong industry standard for Pentium-class computers. It was introduced back in 1993 and is capable of a 132 MB/s data throughput rate at a 33 MHz clock speed. A higher end, server orientated version of PCI has a 66MHz clock speed. The PCI bus also supports burst mode-transfers and full-bus-mastering. Many I/O cards, such as sound cards, video cards, modems, and Ethernet network cards, are available with PCI interfaces. A new variant of PCI, referred to as PCI-X is now appearing in highend applications, and allows a much higher throughput than standard PCI or even 66MHz PCI.

Instead of peripheral devices having to jump through so many hoops to communicate with the CPU, each device can access the CPU local bus directly.

-          Usage: intended for use as an interconnect mechanism between highly integrated peripheral controller components, peripheral add-in boards, and processor/memory systems.

-         Feature: 5.0V and 3.3V signaling environments

Spec & Reference



6. AGP(Accelerated Graphics Port)







It was introduced to speed up graphics display and was faster than PCI when first introduced.

AGP bus is used for the display adapter only.

was introduced to meet consumer demand for high-resolution 3D graphics in home computers. New software programs (especially games) require more and more video bandwidth for fancy textures, high frame rate animations, etc. While the AGP bus employs 66 MHz clocked PCI specifications, it also has the advantage of allowing large amounts of graphics data to be transferred directly between the computer's main memory and the AGP video card. This feature allows the video card to share system memory on demand. The AGP bus is designed strictly for video processing and does not have to share available bandwidth with other connected devices. Most high-performance video cards are now only available as an AGP version.



Spec & Reference




7. Fast Ethernet(100Base-T)



Fast Ethernet is a 100 Mbps version of Ethernet (IEEE 802.3u standard). 100BaseT transmits at 100 Mbps rather than 10 Mbps. Like regular Ethernet, Fast Ethernet is a shared media LAN. All nodes share the 100 Mbps bandwidth. 100BaseT uses the same CSMA/CD access method as regular Ethernet with some modification. Three cabling variations are provided.  

-100BASE-TX: two pairs of high-quality twisted-pair wires

-100BASE-T4: four pairs of normal-quality twisted-pair wires

          -100BASE-FX: fiber optic cables




Backplane of modern embedded systems.  Typically used as a message channel between boards or subsystems. 

+ Readily available hardware, low pin count, existing software stacks, associated software based error management. 

- requires at each end to manage the protocol stack. For applications sending small data payloads, the overhead is burdensome.  Difficult to guarantee deterministic throughput behavior.


Spec & Reference


8. Link 16



Link 16 provides real-time, jam-resistant secure transfer of combat data, voice and relative navigation information between widely dispersed battle elements. Participants gain situational awareness by exchanging digital data over a common communication link that is continuously and automatically updated in real time, reducing the chance of fratricide, duplicate assignments or missed targets. Each participant in the communication link is able to electronically see the battlespace, including assigned targets or threats.







Spec & Reference







9. ETC

COTS(Commercial Off-The-Shelf) bus architecture

While COTS technology is attractive due to its low cost, they are not developed with the same level of rigorous fault tolerance in mind.

Jet Propulsion Laboratory (JPL) has developed a multi-layer fault protection methodology to achieve high reliability in COTS-based avionics systems. This methodology has been applied to the bus architecture that uses the COTS bus interface standards IEEE 1394 and I2C.


- Fast bus

FASTBUS is a sophisticated data acquisition system standard developed by the U.S. NIM Committee in collaboration with the European ESONE Committee (ANSI/IEEE STD 960-1986). FASTBUS was designed to keep features of older important standards while extending the capabilities of data acquisition systems. FASTBUS provides for a more densely packed system, reducing dramatically the per-input cost. This and other design goals have been achieved. FASTBUS meets the requirements of the next generation of data acquisition systems by incorporating several powerful features.

- VMEbus

VersaModule Eurocard BUS) An expansion bus technology developed by Motorola, Signetics, Mostek and Thompson CSF in the early 1980s. Supporting up to 21 cards in a single backplane, VMEbus is widely used in industrial, telecommunications and military applications with products available from several hundred manufacturers worldwide. VMEbus cards (VME cards) come in 3U, 6U and 9U formats.
In 1995, VME64 was introduced, which increased the data and addressing paths from 32 to 64 bits and added several enhancements. However, VME boards can be VME64 compliant and provide less than 64 bits of data transfer and/or addressing. In 1997, VME64x (VME64 eXtensions) added features such as new pin connections, support for 3.3 volts and hot swap capability.

-          bus architecture performance heavily dependent on distribution of computation load, algorithm style http://www.ece.gatech.edu/research/codesign/publications/kkryu/presentation/ryu_62_ppt.pdf



More Comparisons:

USB vs. IEEE-1394
While the two serial buses seem similar, they are intended to fulfill different bandwidth and cost needs. 1394 can move more data in a given amount of time, but is considerably more expensive than USB due to its more complex protocol and signaling rate. Applications that are best suited for 1394 are disk drives, high quality video streams and other high bandwidth applications; all higher end consumer devices. USB is appropriate for middle and low bandwidth applications such as audio, scanners, printers, keyboards, and mice.
USB and 1394 are complementary technologies. 1394 is for devices where high performance is a priority and price is not, while USB is for devices where price is a priority and high performance is not.  http://www.usb.org/faq/ans2.html#q1



IEEE 1394 Firewire


Maximum number of connected devices









Cable length between devices

4.5 m

5 m

Data transfer rate (MB/s)



PC / Mac

Yes / Yes

Yes / iMac only

Embedded power line



Peripheral devices

Set-Top Boxes
Hard Disk drives

PC Monitors
Low-resolution D-Cameras
Low-speed CD-ROM, RW

Relative cost 





-          Interface choices (http://www.usbyte.com/common/Interfaces1.htm#Choices )

         Parallel: Set up is easy.  External.  Slow.

         USB: Set up is very easy. Good performer. Hot swappable. Requires Windows 98 and higher.

         IEEE 1394 FireWire: Set up is easy. Excellent performer. Costly. Requires Windows 98 and higher.

         IDE. Set up is moderately difficult. Requires opening your PC and connecting some cables inside. Performance is much better than parallel- or USB-devices.

         SCSI: Set up is even more difficult than for IDE. Best performer. Best when multiple devices are used. Generally needs a separate SCSI card.

         PC Card(PCMCIA): Set up is easy. Good performance. For notebook use only.





Terminology (referenced from TechWeb)



Bus is a common pathway, or channel, between multiple devices.

1.       Local Bus(processor bus): computers internal bus.  It provides a parallel data transfer path between CPU and main memory and to the peripheral buses.  Address bus+data bus.  Eg) PCI, ISA, EISA, Micro Channel, VL-bus

2.       Peripheral Bus: Eg) NuBus, TURBOchannel, VMEbus, MULTIBUS, STD bus

3.       Network Bus: Eg) Ethernet, FDDI, Token Ring, ATM

Example picture.


Software Bus

A programming interface that allows software modules to transfer data to each other. Although "bus" is traditionally a hardware term for an interconnecting pathway, it is occasionally used in this manner when the focus is on internally transferring large amounts of data from one process to another



Bus topology

1.       Local Bus Topology (bus network)

A network topology that uses a common pathway between all devices.

Limitation of parallel multi-drop buses: frequency, bus width



2. Logical Ring Topology

3. tree topology

4.       Star topology






3 kinds of PC Interfaces

-          special-purpose interfaces - keyboard, sound card, mouse, etc. connectors. They cannot be used for any other device.

-          multi-purpose interfaces - The parallel port (printer port), serial port, universal serial bus (USB), and IEEE 1394 FireWire. They can be used for various peripheral devices, including data storage devices.

-          general-purpose interfaces - The slots on the motherboard, such as PCI and ISA slots, can be used to connect various devices (via the plug-in cards).


(definition of an interface is a hardware and / or software data transmission regulator that controls data exchange between the PC and other devices)


* multi-purpose interfaces

parallel port was originally created for communicating with the printer and thus is called a "printer port". A parallel port (printer port) female connector has 25 pins:

    \  o o o o o o o o o o o o o  /
     \  o o o o o o o o o o o o  /

At least 8 wires are needed for parallel transfer of 8 bits, but the standard IBM-type printer port uses 17 wires for data transfer plus some more to ground the system.  These extra wires are used in intense hand-shaking between the PC and the printer.

The computer puts 8 data bits on the 8 data lines and sends (on a separate line) a so-called strobe signal to the printer to inform it that 8 bits are ready to be transmitted. The printer reads the strobe signal and 8 bits and sends an acknowledgement signal on another wire back to the computer. In this way, the PC printer port does not send data to the printer faster than the printer can accept it. This data is not in any way synchronized by the clock signal and goes as fast as it can. There are five status wires that allow the printer to let the computer know when it is busy processing the data, or is out of paper or experiences a paper jam, etc. Four control wires allow the computer to command the printer to reset itself, to skip the page, etc. This 'standard' parallel port interface can sustain data rates up to 0.15 MB/s, which is faster than the serial port can reliably operate. To connect a parallel port to the printer one has to use a special 25-pin to 36-pin cable. This 'standard' parallel port is currently described in the IEEE1284 standard as a compatibility mode. There are four more newly created modes, which enhances parallel port performance.

-Modification on bidirection:

-          nibble-mode reverse operation

-          byte-reverse operation.

-Faster data transfer rates (widely used in storage devices)

-          EPP (Enhanced Parallel Port)

-          ECP (Extended Capability Port

In EPP design, five more CPU addresses were added to the initial 3 addresses to allow the CPU to transfer data in just one command rather than being involved in various steps of the PC- Printer handshaking. This, along with multiple bytes transfer, available for some EPP hardware designs, improved data transfer rates to almost 2 MB/s (16Mbps) - about 10 times faster than in the standard 'compatibility' mode.   EPP design also allowed block transfer of data and intermixing of data directions (from and to the computer) with no additional delays, which made it suitable for such peripherals as the Zip drive and others.

The ECP interface was meant for even higher data transfer rates than EPP. It utilizes data compression using the RLE (Run Length Encoding) protocol, which is most useful for compressing long sequences of repeated numbers. For example, if the sequence includes 105 zeros, it will be compressed by transmitting the following statement: " here come 105 zeros" instead of sending them all one by one. A relatively loose handshaking protocol, along with the DMA made possible even higher data transfer rates in one direction. To reverse the direction of data transfer, ECP needs several time-consuming steps. This makes the ECP interface less suitable for the external storage devices which often intermix the directions of the data transfer (reading and writing).

Using one port for more than one device used to be achieved via use of mechanical and electrical switch boxes.  Since this architecture is somewhat manufacturer dependent, it is hard to say in advance how many devices it is possible to connect in parallel. Sometime, reversing the order of connections will cause both devices to stop working. If you are lucky, several devices can be connected like this to the same parallel port of the PC.


Serial communication sends one bit at a time. Sending one extra bit for each 8 bits to make sure your data got there, is called a parity bit.  Two common connector types are used for serial communication: the 9-pin connector DB9 and (less often) 25-pin DB25 connector, which is essentially the same. A serial port male connector:

\   o o o o o o  /
\    o o o o    /

The heart of the serial communication technology is the UART (Universal Asynchronous Receiver/Transmitter), which converts parallel streams of data into a single sequence. As soon as the CPU sends the bits to the UART, it is free for another job, and the UART will convert the data into a single sequence and send the bits one at a time over the serial cable using the internal clock to define the time interval for the next bit to be sent. The UART will also send the start bit, the stop bit, and the parity bit (if necessary). Modern PCs can exchange data over the serial port at rates up to 115 KB/s, but this will translate into a maximum data rate of about only 11.5 KB/s without parity and 10.5 KB/s with parity due to the serial communication protocol overhead.





bus mastering

A bus design that allows the peripheral controllers (plug-in boards) to access the computer's memory independently of the CPU. It allows data transfers to take place between the peripheral device and memory while the CPU is performing other tasks.



An interconnecting device that typically has sockets that cards plug into.  This device is used to bridge between various topologies(Ethernet, Token Ring, FDDI, ATM, 1394)


CE(Consumer Electronics)

A broad field of electronics that includes devices such as TVs, VCRs, radios, walkie-talkies, hi-fi stereo, home theater, handheld and software-based games as well as Internet appliances and home computers


SCSI(Small Computer System Interface)

Pronounced "scuzzy." SCSI is a hardware interface that allows for the connection of up to 15 peripheral devices to a single board called a "SCSI host adapter" that plugs into the motherboard, typically using a PCI slot. SCSI is a bus structure itself and functions like a mini-LAN connecting eight or 16 devices. The host adapter counts as one device, thus up to seven or 15 peripherals can be attached depending on the SCSI type. SCSI allows any two devices to communicate at one time (host to peripheral, peripheral to peripheral). SCSI peripherals are daisy chained together. They all have a second port used to connect the next device in line. SCSI host adapters are also available with two controllers that support up to 30 peripherals.
Introduced in 1986 and originally developed by Shugart Associates (see SASI), SCSI is widely used from desktop PCs to mainframes, although most desktop PCs come with IDE drives. The advantage of SCSI in a desktop PC is that a scanner and several other drives (CD-Rs, DVD-RAM, Zip drives, etc.) as well as hard drives can be added to one SCSI cable chain. However, this has become less important as alternate interfaces such as USB and FireWire have become popular.
Until the late 1990s, SCSI hard disks were the only ones used in RAID configurations which provide improved performance and/or fault tolerance. Since the advent of IDE RAID controllers, SCSI and IDE have become more equalized, although SCSI continues to be the drive interface of choice in the server market.
Windows 95/98/NT/2000 and the Macintosh provide internal support for SCSI, but Windows 3.1 and DOS did not. Installing SCSI in a Win 3.1 or DOS machine required adding the appropriate SCSI driver.

There are three types of SCSI signaling.

-          Single-ended SCSI allows devices to be attached to a total cable length of 6 or 3 meters for Fast and Ultra SCSI. Single-ended SCSI is not defined for Ultra2 SCSI and higher.

-          Differential SCSI, or High Voltage Differential SCSI (HVD), is used when devices are spread across a room, because the total cable length is increased to 25 meters. Differential devices cost more than single-ended ones.

-          Ultra2 SCSI introduced Low Voltage Differential signaling (LVD or LVDS) that supports cable lengths up to 12 meters. Single-ended SCSI uses a data line and ground. Both HVD SCSI and LVD SCSI use data low and data high lines to increase transmission distance. However, LVD requires less power and is less costly, because the transceivers are built into the controller chips.


IDE (Integrated Drive Electronics) or ATA(Advanced Technology Attachment)

A popular parallel interface widely used to connect storage devices like hard disks, CD-ROMs and tape drives to a PC. IDE is very popular because it is an economical way to connect peripherals. Starting out with 40MB capacities years ago, 20GB IDE hard disks have become entry level, costing less than half a cent per megabyte.
With IDE, the controller electronics are built into the drive itself, requiring a simple circuit in the PC for connection. IDE drives were attached to earlier PCs using an IDE host adapter card. Today, two Enhanced IDE (EIDE) sockets are built onto the motherboard, and each socket connects to two devices via a 40-pin ribbon cable. Starting with ATA-66 drives, the cable uses 80 wires and 39 pins. It plugs into the same socket with one pin removed.
The IDE interface is officially known as the ATA (AT Attachment) specification. ATAPI (ATA Packet Interface) defines the IDE standard for CD-ROMs and tape drives.  ATA defines the connection and speed for the interface between the hard drive and the computer. ATA/133 is a new industry standard interface that clocks data at 133MBps(or 1.06Gbps; measured trasfer rate up to 114MBps or 912Mbps), faster than the previous generation ATA/100.  Being the least expensive hard drive interface ATA is, in general, slower than SCSI interface, and is used for single user PCs and low-end RAID systems.  All ATA/133 hardware solutions address Big Drives with capacities greater than 137GB. http://www.maxtor.com/Maxtorhome.htm?/products/fastdrive/default.htm

There are two data transfer methods:

-          PIO (Processor Input / Output) has modes 0,1,2,3, and 4, where higher number corresponds to the higher data transfer rate

-          DMA (Direct Memory Access) comes in a single-word and a multi-word (in general, faster) version, and up to three DMA modes (higher number again means higher data rates). 




VGA(Video Graphics Array)

The minimum standard for PC video display, which originated with IBM's PS/2 models in 1987. VGA was initially 640x480 pixels with 16 colors


DMA(Direct Memory Access)

Specialized circuitry or a dedicated microprocessor that transfers data from memory to memory without using the CPU. Although DMA may periodically steal cycles from the CPU, data is transferred much faster than using the CPU for every byte of transfer.


DVI(Digital Visual Interface)

A digital flat panel interface from the Digital Display Working Group (www.ddwg.org). The DDWG was formed to create a universal standard for attaching a flat panel monitor, and DVI is expected to become widely used. Based on TMDS signaling, the final draft of DVI was introduced in early 1999.


Isochronous Data Transfer

This mode implies uniform in time and provides the guaranteed bandwidth by transferring a uniform amount of data every second.  This method is used for, for example, video cameras, where if the error has occurred, it's too late to resend the data again.



An industrial control network for interconnecting sensors, actuators and controllers. The fieldbus protocol stack includes a physical layer, data link layer and application layer.


(Direct Cable Connection) A Windows 95/98 feature that allows PCs to be cabled together for data transfer. DCC actually sets up a network connection between the two machines. Even though it is not a dial-up situation, DCC requires that the Dial-Up Networking function be activated.


(Basic Input Output System) An essential set of routines in a PC, which is stored on a chip and provides an interface between the operating system and the hardware. The BIOS supports all peripheral technologies and internal services such as the realtime clock (time and date). On startup, the BIOS tests the system and prepares the computer for operation by querying its own small CMOS memory bank for drive and other configuration settings. It searches for other BIOS's on the plug-in boards and sets up pointers (interrupt vectors) in memory to access those routines. It then loads the operating system and passes control to it. The BIOS accepts requests from the drivers as well as the application programs.

BIOSs must periodically be updated to keep pace with new peripheral technologies. If the BIOS is stored on a ROM chip (ROM BIOS), it must be replaced. Newer BIOSs are stored on a flash memory chip that can be upgraded via software.


American Wiring Gauge) A U.S. measurement standard of the diameter of non-ferrous wire, which includes copper and aluminum. The smaller the number, the thicker the wire. In general, the thicker the wire, the greater the current-carrying capacity and the longer the distance it can span. Wire used for communications typically ranges from 18 to 26 AWG. For electric service, number 10, 12 and 14 AWG wires are typically used from the electric panel to the outlets. Number 8 and 10 AWG are used for home appliances such as an electric range or dryer.



Interesting Papers


Battery-Efficient Architecture for an 802.11 MAC Processor (http://aspire.ucsd.edu/~klahiri/papers/icc02.pdf)

-          based on a new battery driven power management technique, implemented in the on-chip-bus protocols of the MAC processor.


Fast Performance Analysis of Bus-Based System-On-Chip Communication Architectures http://esdat.ucsd.edu/~klahiri/papers/iccad99.pdf

-          The experimental systems include TCP/IP network interface card sub-system.  Effect of Bus Architectures and Protocols on System Performance shown.







Third Generation I/O architecture:





High-Performance Serial Interconnect Targeted For Intra-System Communications





Q6: How does USB OTG compare with 1394? Does it compete with it?
A6: Since USB On-The-Go is targeted toward existing USB peripherals, it continues to differ in application focus with 1394, just as USB does today.