Margarita Sanger

FireWire is the trade name given by Apple to a Interface series multiplexed, so known under the standard IEEE 1394 and also known under the name of interface i.LINK, trade name used by Sony. It is about a fast drunk conveying at the same time data and signals controls of different the apparatus S which he connects.

Plug and Play, one can use it to connect all peripheral kinds of greedy in Band-width, in particular of the hard drives and the numerical Camescope S. It allows the power supply of the peripheral, as well as the connection of 63 peripherals per hot bus and their connection/disconnection. One can connect to 1024 buses via footbridges.

FireWire was invented by Apple at the beginning of the Années 1990 and can reach flows of several tens of Mo/s. Its objective clearly posted was to replace in the long term the bus USB, in any case for the peripherals by which circulate of important flows of data.

Origin

FireWire is the name given by Apple. The company Sony names it i.Link , the company Texas Instruments using as for it the term Lynx . FireWire was standardized in 1995 under the reference IEEE 1394.

Technology

FireWire uses a temporal Multiplexage: time is cut out in 125 microsecond old sections (: 8000 cycles a second), data being cut out out of packages. In each section the packages Isochrone S are first of all transmitted (its, video…) then asynchronous packages (computer data). This system guarantees the band-width for the video stream thus avoiding effects of jerks and other losses of quality. Isochronous flows are identified by a channel (maximum: 63), and must all have a package per section; once the emitted isochronous packages the remainder of the cycle is used for the asynchronous packages identified not by a channel but by the identifier of the transmitting peripheral and the identifier of the peripheral recipient.

Connection

FireWire is known as Hot Plug (hot connection); the connection or the disconnection of a peripheral starts a drunk event reset at all the other peripherals: thus everyone knows constantly which is present on the bus. With each drunk reset the peripherals receive an identification number of 0 to N (maximum: 62); that which has the greatest number is elected chief of the bus or root , and it is him in particular which is charged to mark the beginning of the 125 microseconds cycles. Any peripheral can thus be root contrary to the USB where this role is ensured by the computer to which the peripherals are connected.

Although it serf to generally connect hard drives or Video camera S to carry out video assemblies, the Firewire port also can, for specific needs, to be used to connect two machines in network; it thus appears in the part “ Connections network ” of Windows XP and like interface network under the systems using the core Linux or UNIX.

Cables

Two distinct stitchings exist in s400: the format with 6 pins allowing the power supply of the peripherals and the format 4 pins without food. In s800 the connectors have 9 pins. s400 and s800 are compatible: one can connect a peripheral s800 with a s400 by using a cable 9 pins towards 6 pins.

The most widespread cable consists of twisted copper wires. Its maximum length for all the FireWire protocols is of 4,5m. There exists also a transmission by fiberoptic, very expensive but making it possible to reach 100m.

Flows

FireWire makes it possible to have theoretical outputs reaching:

100 Mb/s in version 1 (IEEE 1394a-s100)
200 Mb/s in version 1 (IEEE 1394a-s200)
400 Mb/s in version 1 (IEEE 1394a-s400)

800 Mb/s in version 2 (IEEE 1394b-s800)
1200 Mb/s in version 2 (IEEE 1394b-s1200)
1600 Mb/s in version 2 (IEEE 1394b-s1600)
3200 Mb/s in version 2 (IEEE 1394b-s3200)

The standard IEEE 1394b can also be called FireWire Gigabit or FireWire2. s1200, s1600 and s3200 will probably never be born for the general public.

See too

List of the systems of transmission of information

External bonds

an article of the French Jargon
a complete and clear article on FireWire
FireWire on the site of Apple Computer
FireWire (IEEE-1394), pin functions

Simple: FireWire

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