IEEE 1394

FireWire [ ˌ faɪə waɪə ], i.LINK or 1394 is a bus for serial data transfer.

1394 is the name of the Institute of Electrical and Electronics Engineers, and since the specification of a standard 1995. FireWire is the corresponding trademark of Apple, whose development began in 1986. i.LINK is a trademark of Sony extra. Rights of use of both brands will award the 1394 Trade Association.

Licenses essential patent assigns the MPEG Licensing Administration. The merger was agreed upon by Apple, Compaq, Panasonic, Philips, Sony, STMicroelectronics and Toshiba in 1999.

It was not until the late 1990s, Apple Macintosh, and a few other computers were shipped with FireWire, when Apple surprised with $ 1 license fee per connection. Previously received manufacturer for $ 7,500 a blanket license. Full penetration had reached at that time FireWire DV camcorders, it was followed by a declaration of war by the onset of development of the Universal Serial Bus.

In the spring of 2004, the specification for wireless FireWire was adopted. It provides an additional layer, the Protocol Adaptation Layer (PAL ) for FireWire IEEE 802.15.3 before ( which is a standard for wireless personal area network WPAN). The plan is to connect as DVD players and sound systems wirelessly to each other and to a wired network.

  • 6.1 IEEE 1394a ( "FireWire 400")
  • 6.2 IEEE 1394b ( "FireWire 800" )
  • 6.3 IEEE 1394 to 2008 ( "FireWire S3200 " )


The underlying idea for FireWire goes back at Apple until 1986; However, it took almost a decade until a standard has been adopted. Originally (1995 ) it was the three speed classes S100, S200 and S400 for cable connections with the well-known six- pin connectors, also S25 and S50 for FireWire backplanes. In 2000 was added with IEEE 1394a said Sony " i.Link " four-pin connector. Furthermore, IEEE 1394a includes various fixes and performance improvements with continued maximum S400. In 2001, Apple was awarded by the Academy of Television Arts & Sciences with the Technology Emmy for the " important role played by the FireWire technology in the television industry ." Since 2002, the successor IEEE 1394b with S800, S1600 and S3200. He introduces a new type of signaling and new cable with nine pin connectors. Since 2003 S800 hardware is available, which is usually marketed as " FireWire 800". The maximum cable length has been increased significantly by 100 m, thanks to the new encoding method 8b10b. Currently just stands on the introduction of S3200 with a transfer rate of 3.2 Gbit / s over the previous S800 cable.


A maximum of 63 possible devices per bus. FireWire IEEE 1394b supports a ring topology. Up to 1023 buses can be connected by bridges, so that a total of 63 · 1023 = 64 449 devices can be connected. The maximum length of a S400 - connection between two devices is 4.5 meters. With the use of S200, the maximum distance increased to 14 yards. With FireWire IEEE 1394b than other connection types network cable, plastic and fiberglass have been defined which allow a cable length between devices of up to 72 meters. Unlike the Universal Serial Bus (USB) allows instant communication between all FireWire devices to each other (peer -to-peer ) without a host.

Transfer rate

The numbers behind the S or " FireWire" give the rounded transfer rate in megabits per second again. The exact data rate of the basic version (S100 ) is 98.304 million bits per second ( bit / s ≈ 12 MB / s).

Areas of application

Main areas of application

Is used FireWire, especially in the sound and video equipment ( professional audio and video cards ), but also for connecting external storage such as DVD burners, hard drives, or for connection of consumer electronics components, such as Sony under the name "i.LINK" and Yamaha " mLAN". Also a lot of audio interfaces for use in music production are offered for the FireWire port.

To the data transfer rate of modern hard drives ( about 560 Mbit / s with modern 2400 Gb models) To use in external enclosures, the use of the new nine- pin FireWire 800 ( 1394b) is necessary because the conventional FireWire 400 ( 1394a) 400 Mbit / s is limited. USB 2.0 is 480 Mbit / s nominally faster. These two FireWire 400 and USB 2.0 theoretically possible transfer rates are not achieved independently from the hard disk by the protocol overhead. The Bridge chips in the external enclosures limited initially both FireWire and USB. In actual cases, the transfer rates in both cases at about 240 Mbit / s Firewire 800 720 Mbit / s and higher can be achieved. A faster alternative to FireWire 800 are external SATA enclosure, then do without Bridge chips and thus can directly access the hardware.

The power supply via FireWire is specified at 1.5 amps at 8 to 33 volts. External hard drives can therefore easily be operated without its own power supply to a six - or nine- pin FireWire port. USB is a maximum of 0.5 amps at 5 volts, however, not designed for the high inrush current of hard disks and therefore makes at least a precise technical preparation is required.

Automotive industry

The industry association IDB Forum is committed to the use of FireWire interfaces for multimedia systems in automobiles. The use is to complement the already established interfaces such as MOST bus and allow the user to connect standard devices such as video cameras in the car.

Since automotive connectors must meet specific requirements, special connectors have been defined by the IDB Forum. The IDB - 1394b connector is based on the nine -pin IEEE - 1394b, but extends it with a snap - locking system that prevents cable waste. Furthermore, a lead frame is defined, which guarantees the mechanical stability of the jack.

Device addressing and bus management

FireWire knows no defined central host. Unlike USB, each device has the technical potential to become controller. Node IDs and task distribution in the bus management to be every time a device is added or removed from the bus, automatically negotiated between all devices.

Addressing consists of a total of 64 bits and is the standard ISO / IEC 13213 borrowed (ANSI / IEEE 1212 ). Of these 10 bits for network IDs (segment IDs ) and 6 bits for node IDs are assigned. The remaining 48 bits are used to address the device resources (memory, registers) used:

The IEEE 1394.1 for coupling multiple bus segments has been adopted since 2001. However, the concrete implementation in bus bridges requires special FireWire chipsets that can, in contrast to the previously used hardware address more than just a local bus segment. Deficiency need for such a large FireWire networks are these specific ICs currently (January 2010 ) is not available on the market, so that IEEE 1394.1 currently can not be used.

The device with the highest node ID of a segment is the root node. It is responsible for asynchronous arbitration and, as so-called Cycle Master, for the synchronization of all devices for isochronous transfers. If a device is available with appropriate skills on the bus, there is also the Isochronous Resource Manager to manage channels and bandwidth, the bus manager, among others, for optimization of bandwidth and the power manager for controlling power saving functions.

Key Features

IEEE 1394a ( "FireWire 400")

IEEE 1394b ( "FireWire 800" )

Features such 1394a with the following additions and changes:

  • 800 Mbit / s transmission bandwidth
  • New neunadriges cable and new plug
  • New arbitration method (protocol) BOSS (Bus Ownership / supervisor / selector)
  • Other signal coding and signal level, "beta mode"
  • Backwards compatibility with 1394a by bilingual chips ( also operating exclusively in the new " beta " mode possible, thereby, however, no backward compatibility more)
  • Allows the use of different cable materials (for example glass fiber, UTP)
  • Allows longer cable connections ( depending on the cable medium, for example, 100 m when using UTP cables to S100)

IEEE 1394-2008 ( "FireWire S3200 " )

In October 2008, a completely revised version of the standard was published under the name IEEE 1394-2008. It summarizes the basic standard IEEE1394-1995 and the two extensions 1394a -2000 and IEEE 1394b - 2002 together in a consistent document. Moreover Association were discovered and eliminated numerous errors in the original standards of the members of the 1394 Trade. As a major innovation, the electrical specification for a transmission bandwidth of 3.2 Gbit / s has been added. IEEE1394 - 2008 is now the current version of the FireWire standard, the older documents of the IEEE to be will no longer be used.

Security Issues

The OHCI specification ( Open Host Controller Interface) includes a mode for FireWire controller, read in the FireWire devices to the main memory of a computer or to override them. If this mode is configured by a driver, read and write requests are executed autonomously by the hardware, without involving software on this computer. This allows extensive control of the computer by other on FireWire bus connected node. At least in the default configuration include Windows, FreeBSD, Mac OS and Linux prone.

Pin assignment

Note that, in cables with two connectors, the data lines TPA and TPB are crossed, that is, goes to TPA TPB and TPB - TPA hits.

The pin assignment of IEEE 1394 pin headers on motherboards is not standardized across manufacturers and therefore deviates from a rule of this table. Common are both 2 × 5 -pin and 2 x 8-pin pin header.

This also applies to the non-standard circular connectors to high-priced measuring and sensor technology. Despite across companies the same connector, there are different pin assignments.