firewire report upload

8/2/2019 Firewire Report Upload

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ABSTRACT

Firewire is one of the fastest peripherals ever developed which makes it great for use in

multimedia peripherals such as digital video cameras and other high speed devices like the latest

hard disk drives and printers. It provides an inexpensive, high speed method of interconnecting

digital devices. FireWire800 doubles the throughput of the original technology dramatically

increases the maximum distance of FireWire connections, and supports many new types of

cabling. The FireWire roadmap outlined is assumed to take upto a staggering rate of 3200Mbps

from the theoretical 1660Mbps.that is 3.2 gigabits per second that will make the FireWireindispensable for transferring massive data files and for even the most demanding video

applications, such as working with uncompressed high definition video or multiple standard

definition video streams.

FireWire inspired a new generation of consumer electronics devices from many companies,

including Canon, Epson, HP, Iomega, JVC, LaCie, Maxtor, Mitsubishi, Matsushita (Panasonic),

Pioneer, Samsung, Sony and Texas Instruments. Products such as DV camcorders, portable

external disk drives and MP3 players like the Apple iPod would not be as popular as they aretoday with-out FireWire.


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TABLE OF CONTENTS

PREFACE

ACKNOWLEDGEMENTABSTRACT

FIREWIRE

INTRODUCTION TO FIREWIRE

DEFINITION

BASIC HISTORY

CABLES AND CONNECTORS

LIST OF FIGURE

1394-ARCHITECTURE

1394-TOPOLOGY

1394-LAYERS

TYPES OF FIREWIRE

FIREWIRE 400

FIREWIRE 800

THEIR DIFFERENCES

APPLICATIONS

FAILURE AND CAUSES

FIREWIRE:LATEST VERSION

INTRODUCTION TO IEEE- 1394

NEED FOR HIGH-SPEED DATA TRANSFER MEDIUM

ITS KEY FEATURES

1394-ARCHITECTURE

TOPOLOGY

LAYERS

BUS MANAGEMENT

ADVANTAGES AND DRAWBACKS

CONCLUSIONS AND RECOMMENDATIONS

REFERENCES


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FIREWIRE:

INTRODUCTION

Firewire is a way to connect different pieces of equipment, so they can easily and quicklyshare

information.It is a method of transferring information between digital devices especially audio

and video equipment.

It can connect upto 63 devices to Firewire Bus.

Windows OS and Mac OS both support it. [1]

The connection between I/O module in a computer system and external devices can be either

pointto- point or multipoint.

A point to- point interface provides dedicated line between the I/O module and

the external device. On small systems(like PCs)typical point-to-point links

include keyboard,printer and external modem.

A multipont external interfaces are used to support external mass storage

devices(disk and tape drives) and multimedia devices(CD-ROMs,video,audio)

With processor speed reaching GHz and storage devices holding multiple gigabits, the I/O

demands for personal computers, workstation and servers are formidable. Yet the high-speed I/Otechnologies that have been developed for mainframe and supercomputers systems are too

expansive and bulky for use on these smaller systems. Accordingly there has been great interest

in developing a high-speed alternative to SCSI, USB and other small-system I/O interfaces. The

result is the IEEE standard 1394, for a high-speed performance serial bus, commonly known as

Firewire.

Firewire has number of advantages over older I/O interfaces .It is very speedy, low cost , and

easy to implememt. Infact Firewire is finding favour not only for computer systems

but also on consumer electronics products such as digital cameras, VCRs,television where it is

used to transport video images which are increasinly coming from digitized sources.

One of the strengths of the Firewire interface is that it uses serial transmission rather than

parallel. Parallel interface such as SCSI required more wires, which means wider more expensive


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cables and wider more expensive connectors with more pins to bend or break. A cable with more

wires requires shielding to prevent electrical interference between wires. Also, with parallel

interface synchronization between the wires become a requirement a problem that gets worse

with increased cable length.

In addition computers are getting physically smaller even as they expand in computing power

and I/O needs. Handheld and pocketsize computers have little room for connectors yet need high

data rates to handle images and video.

The intent of Firewire is to provide a single I/O interface with a simple connectors that can

handle numerous device through a single port, so that the mouse, laser printer, external disk

drive, sound, and local area network hooks up can be replaced with this single connectors. The

connectors is inspired by the one used in the Nintendo Game boy. It is so convenient that the

user can reach behind the machine and plug it in without looking.

Firewire is one of the fastest peripherals ever developed,which makes it great for use with

multimedia peripherals such as digital video cameras ansd other high speed devices like the latest

hard disk drives and printers.It provides an inexpensive , high speed method of interconnecting

digital devices. Firewire 800 doubles the throughput of the original technology,increases the

maximum distance of firewire connections and supports many new types of cabling. [2]

WHATS THAT:

FireWire is a high-performance connection standard for personal computers and consumerelectronics that makes USB look sluggish. FireWire can move large amounts of data between

computers and peripheral devices at transfer rates of 100, 200 and 400 Mbps (12.5, 25 and 50

megabytes per second, respectively). In simpler terms, it's a heck of a lot faster than USB.


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At such speeds, you could, for instance, plug in a digital camcorder and transfer video data into

your Mac as a pure digital signal without going through the usual digital-to-analog and analog-

to-digital conversion process. FireWire also supports device-to-device transfers for which you'd

not even need your computer. Want to transfer digital video data from your digital camera or

camcorder to a digital VCR? No problem -- if the manufacturers of such devices build them to

take advantages of FireWire's capabilities.

Like USB, FireWire is hot pluggable; up to 63 devices (using cable lengths up to 14 feet) can be

attached to a single bus and connected and disconnected as needed. FireWire cables are easy to

connect because there's no need for device IDs, jumpers, DIPswitches, screws, latches, or

terminators.

FireWire speeds up the movement of multimedia data and large files and enables the connection

of digital consumer products -- including digital camcorders, digital videotapes, digital

videodisks, set-top boxes and music systems -- directly to your computer. The technology allows

for video capture directly from both new DV camcorders with built-in FireWire ports, and from

older analog-only equipment using A/V to FireWire converters.

FireWire was developed with streaming digital media in mind. The technology allows for

isynchronous transport, meaning that any two devices on the bus can have guaranteed

bandwidth through which to pass data.

Besides the aforementioned products, you can also get FireWire-savvy scanners, storage devices,

printer interface cards, A/V converters, digital audio mixers and printers. Of course, you may not

have the time, desire, or, most importantly, money to indulge in such extravagances, but, hey, it's

possible.


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CABLES AND CONNECTORS

Firewire serial interface uses a simple cable with two types of small and inexpensive connectors:4-pin and 6-pin connectors - to carry multiple channels of digitalvideo and video data

and contrl information plus the power.

1. 6-pin to 6-pin cable:This cable draws power from the Firewire Bus and is most commonly used for

connecting to devices such as Firewire Hard Drives, Firewire CD-RWs and other

1394 computer peripherals.

2. 6-pin to 4-pin cable:This cable DOESNOT draw power from the Firewire Bus it is connected to and is

usually used to connect DV cameras or other selfpowered devices.

3. 15-pin to 6-pin adapter:Used to connect to a PCMCIA Cardbus Card.The other end of a cable is a

standard 6-pin(male) connector for connecting to typical Firewire Devices

including Hard Disks and other storage peripherals. Cardbus Cards DO NOT

provide power to Firewire devices.

4. 15-pin to 4-pin adapter:Used to connect to a PCMCIA Cardbus Card. The other end of a cable is a

standard 4-pin (male) connector, most often used to connect to a video camera.

Cardbus Cards DONOT provide power to Firewire


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Firewire cables are available at many electronics stores and may be called IEEE 1394

cables and they come in many lengths, most popular are 0.7 m (2ft), 2 m (6.5ft) and 4.5 m (15ft).

FIREWIRE 400 & FIREWIRE 800:

With more than 30 times the bandwidth of the popular USB 1.1 peripheral standard, FireWire

400 has been the gold standard for high-speed data transfer. Apple was the first computer

manufacturer to include FireWire across its entire product line. And now Apple has upped the

ante yet again, effectively doubling data throughput with its implementation of the IEEE 1394b

standard, FireWire 800, available on the 17 -inch PowerBook G4 and the Power Mac G4.

Twice as fast:

With its high data-transfer speed, FireWire is the interface of choice for todays digital audio and

video devices, as well as external hard drives and other high-speed peripherals. Now transferring

data at up to 800 Mbps, FireWire 800 delivers more than double the effective bandwidth of the

USB 2.0 peripheral standard. That means you can send more than a CDs worth of data every ten

seconds.

Twenty times as far:

FireWire 400 delivers data over cables of up to 4.5 meters in length. Using professional-grade

glass optical fiber, FireWire 800 can burst data across 100-meter cables. So you could toss that

CD more than the length of a football field every ten seconds. Whats more, you dont even


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have to have a new computer or device to gain the length. As long as both devices are connected

to a FireWire 800 hub, you can connect them via super-efficient glass optical cable. That means

you could put a camera on the field connected directly to a Mac in the press box. Or set up a

killer digital audio studio with Macs in one room and recording interfaces in another with no

latency loss from the extra cable length. The short about 5 meters cable distance and the

lack of peer-to-peer connectivity of USB 2.0 limits its usefulness in deployments that require

long haul cabling, such as sound stages and studios.

DIFFERNCES BETWEEN FIREWIRE 400 & FIREWIRE 800:

With the development of FireWire 800, the question on everyones mind is, what is going to

happen to your legacy devices? Existing peripherals and devices are going to continue to operate.

The performance will remain the same for your legacy FireWire devices operating at the original

FireWire 400 speed.

Essentially, the main difference between FireWire 800 and FireWire 400 can be summed up in

one wordspeed. FireWire 800 offers impressive results, with speeds up to 100MB/s, though

current drive technology limits this to 55MB/s (maximum sustained throughput) for a single

drive, and up to 100MB/s (maximum sustained throughput) per bus in RAID 0 configurations.

Other key advancements include the support of increased cabling distances and newly enhanced

arbitration architecture. Utilizing cables constructed of professional-grade glass optical fiber,

when both devices are connected via a FireWire 800 hub, FireWire 800 can burst data across 100

meters of cable.

The new arbitration scheme greatly improves on the existing architecture by incorporating

advanced 8B10B data encoding (based on codes used by Gigabit Ethernet and Fiber Channel),

which reduces signal distortion, and also improves the arbitration time by prepping while the

current data is being sent, allowing the data to be sent as soon as the current transmission is

completed. [3]


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ITS APPLICATIONS :

The intent of firewire is to provide a single I/O interface with single connectors that can

handle numerous device with single port.

Firewire cables are easy to connect because there is no need of device IDs, jumpers,

DIPswitches, screws, latches or terminators.

Firewire can transfer the multimedia and also enables the connection of digital consumer

products- digital camcorders, ipods, videodisks and music systems directly to computer.

DRAWBACKS OF FIREWIRE:

A typical failure scenario is as follows: The user attaches a FireWire storage device to the

computer. The user expects the device to mount on the desktop, but this does not occur.

Repeated attempts to mount the storage device (usually by connecting and disconnecting the

FireWire cable) produce the same results. Ultimately, the user attempts to mount other FireWire

devices on the same port without success, and consequently verifies that the port is no longer

functional. Various attempts to resolve the situation may be attempted, all without success. This

may include machine rebooting, Parameter RAM resetting, power disconnection for extended

periods of time, etc.

Its worth noting that the host FireWire port may be on the motherboard (as is the case for most

Apple computers) or it may be on a PCI FireWire host adapter card. The result is the same; the

particular port no longer works. The port may still be capable of supplying power to the attached


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FireWire device, but the device is no longer seen on the desktop or in the various disk

management utilities.

The failure of the hosts FireWire port can produce a very bad day for the user. The knowledge

of possible damage (and consequential repair cost / hassle) to the computer is compounded by

the frustrating inability to mount and use external storage devices.

FAILURE CAUSES:

Loss of power from the port.

Loss of data transmission from the port.

Failure by Electrostatic Discharge (ESD).

Port failure by Bad Cable or Bad Insertion.

Port failure by Firewire cable twisting.

Port failure by induced under/ over voltage condition.

FIREWIRE: ITS LATEST VERSION- 1394:

The latest version of Firewire is IEEE 1394, is fast and achieves speeds upto 800 Mbps , At

some time in furure , that number is expected to jump to unbelievable 3.2 Gbps when

manufacrurers overhaul the current Firewire cables.


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In 1986, the IEEE Microcomputer Standards Committee began unifying various serial bus

implementations to provide a standard for desktop computer applications. Since 1,393 standards

had already been considered, their efforts were called IEEE 1394. Initially the development was

largely undertook by Apple Computer, who called it FireWire, in an attempt to provide an

inexpensive replacement for the SCSI bus.

In September 1994, the 1394 Trade Association was formed to promote and develop the

Interface. This effort resulted in the development of what became the IEEE 1394-1995 Standard

in fall 1995. The 1394 Trade Association has members from both the computer and consumer

electronics industries, and is still actively developing the 1394 interface.

The IEEE 1394 High Performance Serial Bus standard, informally referred to as 1394, provides

the same services as existing IEEE-standard parallel buses at a potentially lower cost. Rather

than transferring data via a parallel interface, such as EIDE and SCSI with expensive cables and

connectors with as many as 68 pins, 1394 requires only four signal conductors in a low cost

interconnecting cable. 1394 also requires considerably fewer I/O pins on host and peripheral

silicon.

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. [4]


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NEED FOR HIGH- SPEED DATA TRANSFER MEDIUM:

The demand for higher throughput on peripheral devices has become crucial with the Growing

multimedia content in PCs such as real-time color video. Digital devices generate Large volumes

of data, especially when high resolution and high quality results are desiredand video makes

theheaviest demands on throughput. To handle the huge amounts of data from digital video and

audio data streams in real time, a high-performance transport medium such as IEEE 1394 is

needed.

Serial interfaces (few wires) typically have advantages over parallel interfaces (many wires) in

applications where the cost of supporting many wires is greater than the cost of the serial

interfaces more sophisticated electrical protocol. Issues such as die size, I/O count, connector

size and cable routing can be optimized to provide the serial interface with a cost/performance

advantage in some high volume applications. Serial interfaces are generally preferred in

applications where the distances between devices complicate the use of parallel interfaces. The

IEEE 1394 high-speed serial bus hardware and software standard describes a digital interface

that enables the interconnection of computers, peripherals, communications equipment and

digital consumer electronics devices in any combination. This technology features real-time data

transfer at rates of 100 to 400 Mbps, with 1 Gbps and higher expected in future-generation


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implementations. IEEE 1394 is designed for use in computer and consumer peripheral products

such as hard disk devices, printers, scanners, DVDs, camcorders, digital cameras, set-top boxes,

stereo systems, TVs and VCRs.

The IEEE 1394 serial bus interface offers scaleable high performance and bridges PC and

consumer electronics with one easy-to-use cable. In addition to handling high data rates, 1394

accommodates time-sensitive video and audio data through isochronous data transfers. The 1394

bus needs no central controller or dedicated host computer for the data transfers, but instead

operates peer-to-peer to allow any device on the bus to initiate transfers on its ownan

important feature for consumer equipment not linked to PCs.

IEEE 1394 improves the performance of consumer video and audio equipment by Replacing

conventional analog connections and the need for costly, imperfect conversions between analog

and digital formats that inject loss and distortion. It is also emerging as the key data channel for

PCs.

IEEE- 1394:- ITS KEY FEATURES:

Among the features contributing to the IEEE 1394s ease of use is its hot plug-inCapability.Equipment can be connected and disconnected without having to turn the Power off. External

peripherals may be hot-plugged. In contrast, conventional computer portsthose for hard drive,

keyboard, mouse, monitor, etc.are not designed for hot plug-in, and can fail or damage the port

if connected while the power is on. The ultimate objective is to make attaching a 1394 device as

easy as plugging a cord into an electrical outlet. In addition, unlike conventional buses, IEEE


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1394 needs no special terminators along the bus and no special settings to assign device

addresses.

A summary of 1394 features includes:

Fast data transfer rates:

100, 200, or 400 Mbps.

Digital interface:

No need to convert digital data into analog and tolerate the loss of data integrity.

Physically small:

The thin serial cable can replace the larger and more expensive interfaces.

Easy to use: elaborate setup.

No need for terminators, device IDs or

Hot plug cable:

Users can add or remove 1394 devices with the bus active, using rugged

connectors and cables.

Scalable architecture:

Able to mix 100, 200, and 400 Mbps devices on a bus.

Self-configuring:

No need for address switches.

Flexible topology:


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Up to 63 devices on up to 1023 buses with a maximum of 16 hops of up to 4.5

meters between each device.

Bus management:

Is efficient for both large and small configurations.

Both asynchronous and isochronous data transfer:

Guaranteed bandwidth with low overhead for isochronous data transfer.

Three layer architecture:

Consistent with IEEE 1212 Control and Status Register Architecture

Specification ensuring future architectural compatibility.

A fair arbitration system:

Allows all nodes appropriate access to the bus.

Peer-to-peer communication:

Supports daisy chaining and branching.

Reduced buffer costs:

Guaranteed delivery of time-critical data reduces costly buffer requirements.

Non-proprietary:

Licensing is not required.


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The 1394a extension to the standard improves the efficiency of the datatransfer

and arbitration mechanisms while remaining backwards compatible to

the original standard.

The 1394b extension of the standard now being developed will extend the

Signaling rate of the original standard allowing 800Mbps, 1600Mbps and higher.

1394- ARCHITETURE:


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The 1394 standard defines two bus categories: backplane and cable.

The backplanebus is designed to supplement parallel bus structures by providing an

alternate serial communication path between devices plugged into the backplane.

The cable bus, which is the subject of this paper, is a "non-cyclic network with finite

branches, consisting ofbus bridges and nodes (cable devices). Non-cyclic means that

you can't plug devices together so as to create loops. 16-bit addressing provide for up to

64K nodes in a system. Up to 16 cable hops are allowed between nodes, thus the term

finite branches.

A bus bridge serves to connect busses of similar or different types; a 1394-to-

PCI interface within a PC constitutes a bus bridge, which ordinarily serves as the

root device and provides bus master (controller) capability.

A bus bridge also would be used to interconnect a 1394 cable and a 1394

backplane bus.

Six-bit Node IDs allow up to 63 nodes to be connected to a single bus bridge; 10

bit Bus IDs accommodate up to 1,023 bridges in a system. This means, as an

example, that the limit is 63 devices connected to a conventional 1394 adapter

card in a PC.

Each node usually has three connectors, although the standard provides for 1 to


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27 connector per a device's physical layer or PHY. Up to 16 nodes can be daisy-chained through

the connectors with standard cables up to 4.5 m in length for a total standard cable length of 72

m. (Using higher-quality "fatter" cables permits longer interconnections.)

Additional devices can be connected in a leaf-node configuration, as shown in figure 1. Physical

addresses are assigned on bridge power up (bus reset) and whenever a node is added or removed

from the system, either by physical connection/disconnection or power up/down

. No device ID switches are required and hot plugging of nodes is supported. Thus 1394 truly

qualifies as a plug-and-play bus.

1394-TOPOLOGY:

The 1394 protocol is a peer-to-peer network with a point-to-point signaling environment. Nodes

on the bus may have several ports on them. Each of these ports acts as a repeater, retransmitting

any packets received by other ports within the node. Figure 1 shows what a typical consumer

may have attached to their 1394 bus.
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The 1394 protocol is a peer-to-peer network with a point-to-point signaling environment. Nodes

on the bus may have several ports on them. Each of these ports acts as a repeater, retransmitting

any packets received by other ports within the node. Figure 1 shows what a typical consumer

may have attached to their 1394 bus.

Because 1394 is a peer-to-peer protocol, a specific host isnt required, such as the PC in USB. In

Figure 1 , the digital camera could easily stream data to both the digital VCR and the DVD-RAM

without any assistance from other devices on the bus.

Configuration of the bus occurs automatically whenever a new device is plugged in.

Configuration proceeds from leaf nodes (those with only one other device attached to them) up

through the branch nodes. A bus that has three or more devices attached will typically, but not

always, have a branch node become the root node. Ill discuss configuration in more detail later

in this article.

A 1394 bus appears as a large memory-mapped space with each node occupying a certain

address range. The memory space is based to the IEEE 1212 Control and Status Register (CSR)

Architecture with some extensions specific to the 1394 standard. Each node supports up to 48

bits of address space (256 Terabytes). In addition, each bus can support up to 64 nodes, and the

1394 serial bus specification supports up to 1,024 buses. This gives a grand total of 64 address

bits, or support for a whopping total of 16 ExaBytes of memory spaceenough for the latest

version of your favorite word processor and perhaps even a file or two!
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TH E LAYERS OF 1394 TOPOLOGY ARE:

The 1394 architecture is consistent with IEEE 1212 Control and Status Register Architecture

Specification, which defines bus functions, address space and registers. The architecture consists

of three layersphysical, link and transactionthat correspond to the lowest three layers of

ISOs Open Systems Interconnection (OSI) model. The physical layer connects to the 1394

connector and the other two layers connect to the application. To implement a specific


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device,additional protocol and application layers must be placed on top of these layers to provide

the unique functionality of particular devices that use 1394 as an interconnect medium.

The three-stacked layers shown in figure 2 implement the 1394 protocol. The three layers

perform the following functions:

PHYSICAL LAYER:

Physical layer of the 1394 protocol includes the electrical signaling, the

mechanical connectors and cabling, the arbitration mechanisms, and the serial

coding and decoding of the data being transferred or received.

The cable media is defined as a three-pair shielded cable. Two of the pairs are

used to transfer data, while the third pair provides power on the bus.

The connectors are small six-pin devices, although the 1394a also defines a four-

pin connector for selfpowered leaf nodes.

The power signals arent provided on the four-pin connector. The baseline cables are

limited to 4.5m in length. Thicker cables allow for longer distances.

CONFIGURATION:

The physical layer plays a major role in the bus configuration and normal

arbitration phases of the protocol.


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. Configuration consists of taking a relatively flat physical topology and turning it

into a logical tree structure with a root node at its focal point

A bus is reset and reconfigured whenever a device is added or removed. A reset

can also be initiated via software.

CONFIGURATION CONSISTS OF;

Bus reset and Initialization,:

A node driving both TPA and TPB to logic 1 signals reset. Because of the

dominant 1s electrical definition of the drivers, a logic 1 will always be

detected by a port, even if its bi-directional driver is in the transmit state. When a

node detects a reset condition on its drivers, it will propagate this signal to all of

the other ports that this node supports. The node then enters the idle state for a

given period of time to allow the reset indication to propagate to all other nodes

on the bus. Reset clears any topology information within the node, although

isochronous resources are sticky and will tend to remain the same during

resets.

Tree identification,:

The tree identification process defines the bus topology. After reset, but before tree

identification, the bus has a flat logical topology that maps directly to the physical topology.

After tree identification is complete, a single node has gained the status of root node. The tree

identification proceeds as follows.


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After reset, all leaf nodes present a Parent Notify signaling state on their data and strobe pairs.

Note that this is a signaling state, not a transmitted packet. The whole tree identification process

occurs in a matter of microseconds. In our example, the digital camera will signal the set-top

box, the printer will signal the digital VCR, and the DVD-RAM will signal the PC. When a

branch node receives the Parent Notify signal on one of its ports, it marks that port as containing

a child, and outputs a Child Notify signaling state on that ports data and strobe pairs. Upon

detecting this state, the leaf node marks its port as a parent port and removes the signaling,

thereby confirming that the leaf node has accepted the childdesignation. The ports marked with

a P indicate that a device, which is closer to the root node, is attached to that port, while a port

marked with a C indicates that a node farther away from the root node is attached. The port

numbers are arbitrarily assigned during design of the device and play an important part in the

self-identification process.

After the leaf nodes have identified themselves, the digital VCR still has two ports that have not

received a Parent Notify, while the set-top box and the PC branch node both have only one port

with an attached device that has not received a Parent_Notify. Therefore, both the set-top box

and the PC start to signal a Parent_Notify on the one port that has not yet received one. In this

case, the VCR receives the Parent_Notify on both of its remaining ports, which it acknowledges

with a Child_Notify condition. Because the VCR has marked all of its ports as children, the VCR

becomes the root node.

Note that two nodes can be in contention for root node status at the end of the process. In this

case, a random back-off timer is used to eventually settle on a root node. A node can also force

itself to become root node by delaying its participation in the tree identification process for a

while

Self-identification.:


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Once the tree topology is defined, the self-identification phase begins. Self identification consists

of assigning physical IDs to each node on the bus, having neighboring nodes exchange

transmission speed capabilities, and making all of the nodes on the bus aware of the topology

that exists. The self-identification phase begins with the root node sending an arbitration grant

signal to its lowest numbered port. In our example, the digital VCR is the root node and it signals

the set-top box. Since the set-top box is a branch node, it will propagate the Arbitration Grant

signal to its lowest numbered port with a child node attached. In our case, this port is the digital

camera. Because the digital camera is a leaf node, it cannot propagate the arbitration grant signal

downstream any farther, so it assigns itself physical ID 0 and transmits a self ID packet

upstream. The branch node (set-top box) repeats the self ID packet to all of its ports with

attached devices. Eventually the self ID packet makes its way back up to the root node, which

proceeds to transmit the self ID packet down to all devices on its higher-numbered ports. In this

manner, all attached devices receive the self ID packet that was transmitted by the digital

camera. Upon receiving this packet, all of the other devices increment their self ID counter. The

digital camera then signals a self ID done indication upstream to the set-top box, which indicates

that all nodes attached downstream on this port have gone through the self ID process. Note that

the set-top box does notpropagate this signal upstream toward the root node because it hasnt

completed the self ID process.

The root node will then continue to signal an Arbitration Grant signal to its lowest numbered

port, which in this case is still the set-top box. Because the set-top box has no other attached

devices, it assigns itself physical ID 1 and transmits a self ID packet back upstream. This process

continues until all ports on the root node have indicated a self ID done condition. The root node

then assigns itself the next physical ID. The root node will always be the highest-numbered

device on the bus. If we follow through with our example, we come up with the following

physical IDs: digital camera = 0; set-top box = 1; printer = 2; DVD-RAM = 3; PC = 4; and the

digital VCR, which is the root node, 5.

Note that during the self ID process, parent and children nodes are also exchanging their

maximum speed capabilities. This process also exposes the Achilles heel of the 1394 protocol.

Nodes can only transmit as fast as the slowest device between the transmitting node and the

receiving node. For example, if the digital camera and the digital VCR are both capable of


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transmitting at 400Mbps, but the set-top box is only capable of transmitting at 100Mbps, the

high-speed devices cannot use the maximum rate to communicate amongst themselves. The only

way around this problem is for the end user to reconfigure the cabling so the low-speed set-top

box is not physically between the two high-speed devices.

Also during the self ID process, all nodes wishing to become the isochronous resource manager

will indicate this fact in their self ID packet. The highest numbered node that wishes to become

resource manager will receive the honor.

Normal arbitration :

Once the configuration process is complete, normal bus operations can begin. To fully

understand arbitration, knowledge of the cycle structure of 1394 is necessary.

A 1394 cycle is a time slice with a nominal 125s period. The cycle master keeps the 8kHz cycle

clock, which is also the root node. To begin a cycle, the cycle master broadcasts a cycle start

packet, which all other devices on the bus use to synchronize their time bases.

Immediately following the cycle start packet, devices that wish to broadcast their isochronous

data may arbitrate for the bus. Arbitration consists of signaling your parent node that you wish to

gain access to the bus. The parent nodes in turn signal their parents and so on, until the request

reaches the root node. In our previous example, suppose the digital camera and the PC wish to

stream data over the bus. They both signal their parents that they wish to gain access to the bus.

Since the PCs parent is the root node, its request is received first and it is granted the bus. From

this scenario, it is evident that the closest device to the root node wins the arbitration.

Because isochronous channels can only be used once per cycle, when the next isochronous gap

occurs, the PC will no longer participate in the arbitration. This condition allows the digital

camera to win the next arbitration. Note that the PC could have more than one isochronous

channel, in which case it would win the arbitration until it had no more channels left. This points


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out the important role of the isochronous resource manager: it will not allow the allotted

isochronous channels to require more bandwidth than available.

When the last isochronous channel has transmitted its data, the bus becomes idle waiting for

another isochronous channel to begin arbitration. Because there are no more isochronous devices

left waiting to transmit, the idle time extends longer than the isochronous gap until it reaches the

duration defined as the sub action (or asynchronous) gap. At this time, asynchronous devices

may begin to arbitrate for the bus. Arbitration proceeds in the same manner, with the closest

device to the root node winning arbitration.

This point brings up an interesting scenario: because asynchronous devices can send more than

one packet per cycle, the device closest to the root node (or the root node itself) might be able to

hog the bus by always winning the arbitration. This scenario is dealt with using what is called the

fairness interval and the arbitration rest gap. The concept is simpleonce a node wins the

asynchronous arbitration and delivers its packet, it clears its arbitration enable bit. When this bit

is cleared, the physical layer no longer participates in the arbitration process, giving devices

farther away from the root node a fair shot at gaining access to the bus. When all devices wishing

to gain access to the bus have had their fair shot, they all wind up having their arbitration enable

bits cleared, meaning no one is trying to gain access to the bus. This causes the idle time on the

bus to go longer than the 10s sub action gap until it finally reaches 20s, which is called the

arbitration reset gap. When the idle time reaches this point, all devices may reset their arbitration

enable bits and arbitration can begin all over again.

LINK LAYER:

The Link layer is interface between the physical layer and the transaction layer.


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The Link layer is responsible for checking received CRCs an dcalculating and appendingthe CRC to transmitted packets.

In addition, because isochronous transfers do not use the transaction layer, the link layer

is directly responsible for sending and receiving isochronous data.

The link layer also examines the packet header information and determines the type of

transaction that is in progress. This information is then passed up to the transaction layer.

The interface between the link layer and the physical layer is listed as an informative (not

required) appendix in the IEEE 1394-1995 specification. In the 1394a addendum,

however, this interface becomes a required part of the specification. This change was

instituted to promote interoperability amongst the various 1394 chip vendors.

The link layer to physical layer interface consists of a minimum of 17 signals that must

be either magnetically or capacitive isolated from the PHY.

A typical link layer implementation has the PHY interface, a CRC checking and

generation mechanism, transmit and receive FIFOs, interrupt registers, a host interface

and at least one DMA channel.

TRANSACTION LAYER:

The transaction layer is used for asynchronous transactions. The 1394 protocol uses a

request-response mechanism, with confirmations typically generated within each phase.

Several types of transactions are allowed.

They are listed as follows:


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Simple quadlet (four-byte) read

Simple quadlet write

Variable-length read

Variable-length write

Lock transactions

Lock transactions allow for atomic swap and compare and swap operations to beperformed.

Transactions can be split, concatenated, or unified.

The split transaction occurs when a device cannot respond fast enough to the transaction

request. When a request is received, the node responds with an acknowledge packet. An

acknowledge packet is sent after every asynchronous packet. In fact, the acknowledging

device doesnt even have to arbitrate for the bus; control of the bus is automatic after

receiving an incoming request or response packet.

The responder node sends the acknowledge back and then prepares the data that was

requested. While this is going on, other devices may be using the bus. Once the responder

node has the data ready, it begins to arbitrate for the bus, to send out its response packet

containing the desired data. The requester node receives this data and returns an

acknowledge packet (also without needing to re-arbitrate for the bus).

If the responder node can prepare the requested data quickly enough, the entire

transaction can be concatenated. This removes the need for the responding node to

arbitrate for the bus after the acknowledge packet is sent.

For data writes, the acknowledgement can also be the response to the write, which

is the case in a unified transaction. If the responder can accept the data fast

enough, its acknowledge packet can have a transaction code of complete instead

of pending. This eliminates the need for a separate response transaction

altogether. Note that unified read and lock transactions arent poss ible, and the

acknowledge packet cant return data [5]

BUS MANAGEMENT:


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Bus management on a 1394 bus involves several different responsibilities that may be

distributed among more than one node. Nodes on the bus must assume the roles of

Cycle master,

Isochronous resource manager,

Bus manager.

CYCLE MASTER:

The cycle master initiates the 125s cycles.

The root node must be the cycle master; if a node that is not cycle master capable

becomes root node, the bus is reset and a node that is cycle master capable is forced to be

the root.

The cycle master broadcasts a cycle start packet every 125s. Note that a cycle start can

be delayed while an asynchronous packet is being transmitted or acknowledged.

.The cycle master deals with this by including the amount of time that the cycle was

delayed in the cycle start packet.

ISOCHRONOUS RESOURCE MANAGER:

The isochronous resource manager must be isochronous transaction capable.

The isochronous resource manager must also implement several additional

registers

These registers include the Bus Manager ID Register, the Bus Bandwidth

Allocation Register, and the Channel Allocation Register


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A node that wishes to transmit isochronous packets performs isochronous channel

allocation. These nodes must allocate a channel from the Channel Allocation

Register by reading the bits in the 64-bit register

. Each channel has one bit associated with it. A channel is available if its bit is set

to logic 1. The requesting node sets the first available channel bit to a logic 0 and

uses this bit number as the channel ID

In addition, the requesting node must examine the Bandwidth Available Register

to determine how much bandwidth it can consume. The total amount of

bandwidth available is 6,144 allocation units.

One allocation unit is the time required to transfer one quadlet at 1,600Mbps. A

total of 4,915 allocation units are available for isochronous transfers if any

asynchronous transfers are used. Nodes wishing to use isochronous bandwidth

must subtract the amount of bandwidth needed from the Bandwidth Available

Register

BUS MANAGER;

A bus manager has several functions, including publishing the topology and speed maps,

managing power, and optimizing bus traffic

.Nodes with a sophisticated user interface that could instruct the end user on the optimum

connection topology to enable the highest throughput between nodes may use the

topology map

Nodes to determine what speed it can use to communicate with other nodes use the speed

map.

The bus manager is also responsible for determining whether the node that has become

root node is cycle master capable. If it isnt, the bus manager searches for a node that is

cycle master capable and forces a bus reset that will select that node as root node

The bus manager might not always find a capable node; in this case, at least the

isochronous resource manager performs some of the bus management functions.


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FIREWIRE VS USB:

While FireWire sounds like USB on steroids, the technologies serve different purposes. FireWire

-- a much cleaner and more advanced spec than USB -- is for peripherals that need maximum

bandwidth. USB is a medium bandwidth connection for peripherals such as digital still cameras,

monitors, keyboards and mice.

But with USB 2.0 looming on the horizon, will FireWire wilt and fade? Possibly, but not likely.

The prediction (that is, the prognosis of Yours Truly) is that, even if version 2.0 does what's

being promised -- and that's probably not going to happen anytime soon -- it and FireWire will

coexist peacefully. It seems doubtful that USB 2.0 will encroach too much on digital video and

audio territory that FireWire has slowly but surely conquered.

Why? FireWire can transfer data point-to-point (one device to another) while USB requires the

computer to server as a go-between. In other words, moving data with USB means you have to

move it from one doohickey to your computer, then transfer it from the computer to the otherdoohickey. FireWire can move data directly from one device to another. Plus, as we mentioned,

FireWire will soon hit speeds of 800 Mbps, late this year or early in 2001. And there's

speculation of speeds of up to 1.6 Gbps a year or two down the road. So expect USB and

FireWire to live together, if not in harmony, at least in some sort of truce.

TOPOLOGY;

The topology of 1394, known as a tree topology, is shown in figure 1 below. Any device can be

connected to any other device, so long as there are no loops. A 1394 network can support up to

63 devices. The devices can be hot swapped. If a device is added or removed, the bus will reset,

reconfigure, and continue operation. If the bus is broken, the two pieces will reset, reconfigure,

and resume operation as two independent busses. 1394 also offers peer-to-peer connectivity, so


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peripherals can talk to one another without intervention from the PC. The PC acts as the host.

Each device is connected to a hub, which provides sockets and power and acts as a repeater.

Hubs can be either self-powered or bus powered. They can also be cascaded. The USB topology

supports up to 127 devices.

SPEED:

USB offers speeds ranging from 1 Mbits per second to 12 Mbits per second. In contrast, the

current IEEE specification 1394-1995 offers speeds starting at 100 Mbits per second and going

up to 400 Mbits per second. P1394b will start at 800 Mbits per second and is defining speeds of

up to 3200 Mbits per second. P1394b is expected to be fully backward compatible with the 100-

400 Mbits per second specification, - connector cable and software.

APPLICATION:

As mentioned previously, 1394 and USB are complimentary technologies. USB is a medium

bandwidth connection for telephony products, digital still cameras, monitors, keyboards, mice,

and other similar I/O devices. In contrast, 1394 is a high-speed bus designed for digital video

cameras, DVD players, mass storage devices, and other peripherals that require greater

bandwidth.

COST:

USB is a very low-cost interconnects technology. Low-speed USB implementations for devices

such as mice and keyboards typically cost less than $1 in OEM quantities, and even the medium-

speed implementations for devices like scanners and modems are in the $1-2 range in OEM


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quantities. Due to relatively lower volumes and higher complexity, 1394 implementations are

currently in the $15 range. This cost is expected to decrease as volume builds over the next few

years

ADVANTAGES OF FIREWIRE:

Firewire 800 vs SCSI:

The SCSI based system has a number of disadvantages to FireWire 800. SCSI based systems

have a parallel interface, which cases it to have very limited connect ability, unlike FireWire that

can connect to almost all computer peripherals. SCSI is still a very expense route for computer

speed and has a maximum capacity per drive of 146GB compared to 500GB for LaCies Big


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Disk. FireWire devices are truly plug and play, unlike SCSI devices which require a device ID,

FireWire devices can be plugged or unplugged without the need to restart your computer.

Firewire 800 vs USB 2.0:

USB 2.0 has a maximum throughput of 480 Mbps, so in theory it is faster than the 400 Mbps

performance of FireWire 400. Due to transfer protocol differences, this isnt necessarily true

depending on the peripheral. However, FireWire 800 clearly doubles the theoretical speed and

immediately delivers better performance with modern drive technology. Additionally, FireWire

is more suitable for time-critical isochronous data transfers that will be necessary for high

definition video.

CONCLUSIONS :Most of the failure modes of FireWire ports are believed to be caused by low quality or worn out

FireWire cables, operator error during device and cable insertion, inadequate PHY port

protection, and improper design of external FireWire devices which causes voltage surges to the

host port.


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CABLE PREVENTATIVES:

Users are encouraged to use high quality FireWire cables.

Users are encouraged to replace worn out FireWire cables.

Never plug a FireWire cable in backwards (although it seems impossible; its been done

many times.)

Dont apply twisting torque to cables that are inserted into sockets.

If a device doesnt mount, do not test the cable on another machine.

HOST PORTS:

Older computers may not have FireWire port protection built into them. This appears to

place them at higher risk of failure.

Recently manufactured computers are likely to have enhanced port protection.

If your port fails while the computer is within warranty, you wont have any problems

getting it repaired.

If your port fails while the computer is out of warranty, an inexpensive solution is to use

a low cost PCI FireWire host card. (assuming you have open slots).


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LOOKING TO FUTURE:

There is currently an effort underway in IEEE working groups to extend the capabilities of the

original 1394-1995 standard. The effort, known as 1394b, will extend the standard by improving

the signaling protocol to allow for more efficient transfer of data. The second, known as 1394b,

will extend the standard further by permitting operating speeds of 800 Mbps and beyond. These

rates will exceed the transfer rates of the EIDE and SCSI parallel interfaces.

Because the pending 1394b standard provides data transfer rates higher than existing low cost

interfaces, it is currently in the running to become the successor to EIDE for storage peripherals.

As such, 1394 is receiving strong backing from technology leaders such asMicrosoft, Intel, and

Apple. Storage companies such as Western Digital, Seagate, Quantum, Maxtor and others have

invested time and resources towards creating the necessary standards to enable attachment of

storage peripherals via the 1394 interface. The hard drive companies have taken a leadership role

in these efforts since the interfacecould become the standard for hard drive attachment in the PC

industry.

The move from analog to digital functionality in consumer electronics will spur the move to

IEEE 1394 in the near future. Confirming the industry consensus, 1999 has been theyear that

1394 became established in consumer applications. Based on the initial success of the Sony

camcorders, other audio/visual products have been introduced. These introductions include:

DVD for television using the MPEG-2 format, DVD as a CDROM, desktop cameras and color

printers.


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Ultimately ATM (Asynchronous Transfer Mode) and IEEE 1394 will drive each other's markets.

ATM will become the worldwide voice/video/data public switched networks.However; ATM is

too expensive for devices such as hard disk drives, cameras and desktop computers. Therefore

IEEE 1394 is a complementary device interface for ATM.

Built on a base of inexpensive implementations, IEEE 1394 will become a high volume

consumer electronics interface. Consumer electronics interfaces tend to be long livedplain old

telephone service (POTS) is over 100 years old, and audio/video coaxial interfaces date from

World War II. Therefore, with ability to span media and maintain software compatibility, IEEE

1394 should enjoy a very long life. If ATM, the next telephone system, lasts at least 100 years,

then IEEE 1394 could be there as well.

Such a high volume interface will enable many new applications. Not only will audio/visual data

be available for computers to manipulate, but a user-friendly command-and-control interface will

span home, vehicle, office and factory products. Existing barriers will gradually be shattered by

the expected growth of IEEE 1394.


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REFERENCES:

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2)

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4)www.howstuffworks.com

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