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FireWire symbol
i.LINK symbol
Connector for FireWire 400,
left four-pin, right six-pin
Connector for FireWire 800
Socket for FireWire 800,
next to it left Ethernet and right USB
Plug-in card for FireWire 400
at the bottom socket for FireWire 400,
above socket for USB

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

1394 is the name of the Institute of Electrical and Electronics Engineers and has been a standard since the 1995 specification . FireWire is the corresponding trademark of Apple , the development of which began in 1986. i.LINK is an additional trademark owned by Sony . Until their dissolution in 2015, the 1394 Trade Association granted usage rights for both brands .

The MPEG Licensing Administration grants usage rights for basic patents . The merger was agreed in 1999 by Apple, Compaq , Panasonic , Philips , Sony , STMicroelectronics and Toshiba .

It wasn't until the late 1990s that Apple Macintosh and a few other computers came with FireWire when Apple surprised everyone with a $ 1 license fee per connection. Previously, manufacturers received a flat-rate license for $ 7,500. At that time FireWire had already achieved complete market penetration with DV camcorders , followed by a declaration of war due to the ongoing further development of the Universal Serial Bus . FireWire is currently no longer playing a role in the market after Apple gradually abandoned the interface in favor of USB and Thunderbolt .

In the spring of 2004, the specification for wireless FireWire was passed. It provided an additional layer, the Protocol Adaptation Layer (PAL), for FireWire over IEEE 802.15.3 (this is a standard for Wireless Personal Area Network , WPAN). It was planned, for example, to connect DVD players and sound systems wirelessly to one another and also to a wired network.


The underlying idea for FireWire at Apple goes back to 1986; however, it took nearly a decade for a standard to be passed. Originally (1995) there were three speed classes S100, S200 and S400 for cable connections with the well-known six-pin plugs, as well as S25 and S50 for FireWire backplanes . In 2000, IEEE 1394a was the addition of the four-pin connector called “i.Link” by Sony. IEEE 1394a also includes various corrections and performance improvements for a maximum of S400. The successor IEEE 1394b with S800, S1600 and S3200 has been available since 2002. He introduces a new type of signaling and new cables with nine-pin plugs. S800 hardware has been available since 2003, usually marketed as "FireWire 800". The maximum cable length has also been increased significantly to 100 m thanks to the new 8b10b coding process. From 2007 the introduction of the S3200 with a transmission rate of 3.2 Gbit / s via the previous S800 cables was due.


A maximum of 63 devices are possible per bus . FireWire IEEE 1394b supports ring topology . Up to 1023 buses can be connected with bridges, so that a total of 63 · 1023 = 64 449 devices can be connected. The maximum length of an S400 connection between two devices is 4.5 meters. When using the S200, the maximum distance increases to 14 meters. With FireWire according to IEEE 1394b, network cables, plastic and glass fibers have been defined as further connection types, which allow a cable length between devices of up to 72 meters. Unlike the Universal Serial Bus (USB), FireWire allows direct communication between all devices ( peer-to-peer ) without a host .

Transfer rate

The numbers behind the S or "FireWire" indicate the rounded transfer rate in megabits per second. The exact data rate of the basic version (S100) is 98,304,000 bit / s = 96,000 × 1024 bit / s = 12,000 × 1024 byte / s.

Areas of application

Main areas of application

FireWire was used in the 2000s primarily in sound and video technology (professional audio and video cards), but also to connect external mass storage devices such as DVD burners , hard drives or to connect consumer electronics components. For example at Sony under the name "i.LINK" and Yamaha with " mLAN ". Many audio interfaces for use in music production were also offered for the FireWire connection.

FireWire 400 (1394a) is limited to 400 Mbit / s. The nine-pin FireWire 800 (1394b) is limited to 800 Mbit / s. USB 2.0 is nominally faster than FireWire 400 at 480 Mbit / s. These transfer rates theoretically possible with FireWire 400 and USB 2.0 are not achieved due to the protocol overhead, for example with an external hard drive. The bridge chips in the external enclosures initially restricted both FireWire and USB. With Firewire 800, 720 Mbit / s and more can be achieved. At that time, a faster alternative to FireWire 800 were external SATA housings, which then managed without bridge chips and thus could directly access the hardware.

The power supply via FireWire is specified with 1.5 amps at 8 to 33 volts. External hard drives can therefore easily be operated without their own power supply unit on a six- or nine-pin FireWire port. With a maximum of 0.5 amps at 5 volts, however, USB up to 2.0 is not designed for the high inrush current of hard drives and therefore requires at least precise technical preparation.

With the introduction of USB 3.0 in 2008, FireWire was considered obsolete. The gross data rate of 5 GBit / s also exceeded that of the FireWire S3200. USB 3.1, which was specified in 2015, already achieves 10 GBit / s. It provides electrical power in the range of 10 watts (5 V × 2 A) to 100 watts (20 V × 5 A).

Automotive industry

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

Since the connectors in the automobile have to meet special requirements, the IDB Forum has defined special connectors. The IDB-1394b connector is based on the nine-pin IEEE-1394b, but extends it with a snap lock to prevent cable dropping. In addition, a guide frame is defined that guarantees the mechanical stability of the bush.

Device addressing and bus management

FireWire does not have a defined central host. In contrast to USB, every device has the technical requirements to become a controller. Node IDs and task distribution in bus management are automatically negotiated between all devices every time a device is added to or removed from the bus.

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

Bit 0-9 (10 bit) Bit 10–15 (6 bit) Bit 16–63 (48 bit)
Bus ID (segment ID) Device addressing (node ​​ID) further addressing

The IEEE 1394.1 standard for coupling multiple bus segments has been adopted since 2001. The actual implementation in so-called bus bridges, however, requires special FireWire chipsets which, in contrast to the hardware previously used, can address more than just one local bus segment. Due to the lack of demand for such large FireWire networks, these special ICs are currently (January 2010) not available on the market, so that IEEE 1394.1 cannot be used at the moment.

The device with the highest node ID of a segment is its root node. It is responsible for asynchronous arbitration and, as a so-called cycle master , for synchronizing all devices for isochronous transfers. If a device with the appropriate capabilities is available on the bus, there is also the Isochronous Resource Manager for managing channels and data rates, the Bus Manager for optimizing the data rate, and the Power Manager for controlling power-saving functions.

main features

Tree structure with FireWire

IEEE 1394a ("FireWire 400")

  • 100, 200 or 400 Mbit / s transfer rate
  • Devices can be connected during operation and are automatically recognized: " hot plug " and "hot unplug"
  • Integrated power supply for devices (8 to 33 V DC, 1.5 A, max. 48 W), except for the four-pole variant, which does not supply any current
  • Connection via Shielded Twisted Pair ( STP )
    • thin and therefore flexible six-wire cable (four wires for data transfer, two for power supply) or
    • four-wire cable (four wires for data transfer, no power supply lines)
  • no terminators required at the cable ends
  • Data transmission in half duplex method
  • 4.5 meters max. Distance between two devices (at 400 Mbit / s)
  • Total length of a “ daisy chain ” line maximum 72 meters
  • Up to 63 devices can be connected per bus (up to 16 per "daisy chain" strand)
  • up to 1023 buses via bridges zusammenschließbar
  • packet-oriented data transmission
  • fast isochronous mode
  • Device addressing automatically (no jumper settings on the devices or ID switches necessary)

IEEE 1394b ("FireWire 800")

Features like 1394a with the following extensions and changes:

  • 800 Mbit / s transfer rate
  • new nine-core cable and new plugs
  • new arbitration procedure (protocol) BOSS (Bus Ownership / Supervisor / Selector)
  • different signal coding and signal level, "beta mode"
  • Downward compatibility to 1394a through bilingual chips (operation only possible in the new "beta mode", however, no more downward compatibility)
  • allows the use of different cable materials (e.g. fiber optic cables , UTP )
  • allows longer cable connections (depending on the cable medium, for example 100 m when using UTP cables up to S100)

IEEE 1394–2008 ("FireWire S1600 and S3200")

In October 2008, a completely revised version of the standard was published under the name IEEE 1394-2008. It combines the basic standard IEEE1394-1995 as well as the two extensions IEEE1394a-2000 and IEEE1394b-2002 in one consistent document. In addition, members of the 1394 Trade Association discovered and fixed numerous errors in the original standards. The electrical specification for a transmission rate of 3.2 Gbit / s was added as a major innovation. IEEE1394-2008 is the now valid version of the FireWire standard, the older IEEE documents should no longer be used in the future. FireWire S3200 was discontinued in 2012.

Security issues

The OHCI specification ( Open Host Controller Interface ) includes an operating mode for FireWire controllers in which FireWire devices can read out or overwrite the main memory of a computer ( Direct Memory Access, DMA ). If this operating mode is configured by a driver, read and write requests are carried out autonomously by the hardware, without involving software on this computer. This enables extensive control of the computer by other participants connected to the FireWire bus. At least in the default configuration, Windows , FreeBSD , macOS and Linux are vulnerable; But since a hardware mechanism comes into play, no operating system has to be started in the actual sense - a BIOS screen is sufficient.

Pin assignment

It should be noted that on cables with two plugs, the data lines TPA and TPB are crossed, i.e. TPA + goes to TPB + and TPA− goes to TPB−.

pin 1394a
- 1 8th positive supply voltage VP, up to 30 volts, usually +12 volts
- 2 6th GND
1 3 1 TPB−
2 4th 2 TPB +
3 5 3 TPA−
4th 6th 4th TPA +
- 2 5 Screen TPA
- 2 9 Screen TPB
- - 7th not used

The pin assignment of IEEE 1394 pin connectors on motherboards is not standardized across manufacturers and therefore usually deviates from this table. Both 2 × 5-pin and 2 × 8-pin header connectors are common. Channel A can be identified by the (positive) open circuit voltage: TPA + as well as TPA- are subjected to TPBIAS. TPB is passively terminated. According to the specification, VP / GND can be loaded with 1.5 amps, i.e. up to 45 watts depending on the VP implemented. The shielding of twisted pair A and the shielding of twisted pair B in the cable are correctly isolated from each other, only then connected in a star shape with each other and with GND, but not with the outer cable shield. This connection is only made in the four-pin i.Link connector.

There are also different pin assignments for the non-standard-compliant, but cross-company, same circular connectors on high-priced measurement and sensor technology.


  • Franz-Josef Lintermann, Udo Schaefer, Walter Schulte-Göcking, Klaas Gettner: Simple IT systems. Textbook / specialist book . 5, 1st corrected reprint edition. Bildungsverlag EINS, 2008, ISBN 978-3-8237-1140-7 (pages 72-75).

Web links

Commons : FireWire  album with pictures, videos and audio files

Individual evidence

  1. IEEE SA - 1394 WG . Institute of Electrical and Electronics Engineers. Archived from the original on December 30, 2011. Info: The archive link was automatically inserted and not yet checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved November 7, 2011. @1@ 2Template: Webachiv / IABot /
  2. What is FireWire? . 1394 Trade Association. Archived from the original on April 4, 2014. Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved November 7, 2011. @1@ 2Template: Webachiv / IABot /
  3. ^ FireWire - Software Licensing and Trademarks . Apple. Retrieved November 7, 2011.
  4. License Agreements for i.LINK (aka IEEE1394) Trademark . Sony. Retrieved November 7, 2011.
  5. ^ 1394 Trade Association . 1394 Trade Association. Retrieved March 1, 2018.
  6. 1394 Introduction . MPEG Licensing Administration. Retrieved November 7, 2011.
  7. Patent Pools (PDF; 46 kB) United States Patent and Trademark Office. Archived from the original on October 21, 2011. Info: The archive link was automatically inserted and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. Retrieved November 7, 2011. @1@ 2Template: Webachiv / IABot /
  8. CNET: Apple licensing FireWire for a fee . Retrieved November 7, 2011.
  9. Apple caves in over FireWire licensing . The Register. Retrieved November 7, 2011.
  10. USB should be 40 times faster . Heise publishing house. October 13, 1999. Retrieved November 7, 2011.
  11. ^ The tragedy of FireWire . Ars Technica: The tragedy of FireWire. June 22, 2017. Accessed March 1, 2018.
  12. ,  ( page no longer available , search in web archivesInfo: The link was created automatically marked as defective. Please check the link according to the instructions and then remove this notice.@1@ 2Template: Dead Link /  
  13. Tame USB hard drive. In: Heise online . January 29, 2011 . Retrieved June 11, 2011.
  14. FireWire / IEEE 1394 / i.Link., accessed on May 25, 2016 .
  16. Archived copy ( memento of the original from March 5, 2005 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice. @1@ 2Template: Webachiv / IABot /
  17. Archive link ( Memento of the original from March 26, 2010 in the Internet Archive ) Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.  @1@ 2Template: Webachiv / IABot /