Firewire Simplified

What is Firewire?
The IEEE 1394 interface commonly referred to as FireWire(Apple) is a serial bus interface standard for high-speed communications and real-time data transfer. FireWire is capable of connecting up to 63 peripherals devices. It allows peer-to-peer device communication such as communication between a scanner and a printer without having to use system memory or the CPU. FireWire also supports multiple hosts per bus. It is designed to support Plug and play and hot swapping. Here is a look at the various Firewire formats:

FireWire 400 (IEEE 1394-1995)
The original release of IEEE 1394-1995 specified what is now commonly referred to as "FireWire 400".
Firewire 400 can transfer data between devices at 100, 200, or 400 Mbit/s half-duplex data rates. These different transfer modes are referred to as S100, S200, and S400. As with USB, there are limitations in cable length. For Firewire, the distance is limited to 4.5 meters (14.8 ft), although up to 16 firewire cables can be linked or "daisy chained" together using active repeaters; external hubs, and even internal hubs which are sometimes present in FireWire equipment. The S400 standard limits any configuration's maximum cable length to 72 metres (240 ft). The 6-circuit connector is commonly found on desktop computers, and can supply the connected device with power.

FireWire 800 (IEEE 1394b-2002)
IEEE 1394b-2002 introduced FireWire 800 (Apple's name for the 9-circuit "S800 bilingual" version of the IEEE 1394b standard). The 800 specification and corresponding products allow a transfer rate of up to 800 Mbit/s.  Firewire 800 is backwards compatible to the slower rates and 6-circuit alpha connectors of FireWire 400. However, while the IEEE 1394a and IEEE 1394b standards are compatible, FireWire 800's connector, referred to as a beta connector, is different from FireWire 400's alpha connectors, making legacy cables incompatible. The complete IEEE 1394b specification supports data rates of up to 3200 Mbit/s (i.e. 400 megabytes/s) over beta-mode or optical connections up to 100 meters (330 ft) in length. Standard Category 5e unshielded twisted pair supports 100 meters (330 ft) at S100.

FireWire S1600 and S3200
In December 2007, the 1394 Trade Association announced that products would be available before the end of 2008 using the S1600 and S3200 modes that, for the most part, had already been defined in 1394b. 1394-2008 The 1.6 Gbit/s and 3.2 Gbit/s devices use the same 9-circuit beta connectors as the existing FireWire 800 and will be fully compatible with existing S400 and S800 devices. It will compete with the forthcoming USB 3.0.

FireWire S800T (IEEE 1394c-2006)
IEEE 1394c-2006 was published on June 8, 2007. It provided a major technical improvement, namely new port specification that provides 800 Mbit/s over the same 8P8C (Ethernet) connectors with Category 5e cable, which is specified in IEEE 802.3 clause 40 (gigabit Ethernet over copper twisted pair) along with a corresponding automatic negotiation that allows the same port to connect to either IEEE Std 1394 or IEEE 802.3 (Ethernet) devices.

Future enhancements (including P1394d)
A project named IEEE P1394d was formed by the IEEE on March 9, 2009 to add single mode fiber as an additional transport medium to FireWire. Other future iterations of FireWire are expected to bring a bump in speed to 6.4 Gbit/s and additional connectors such as the small multimedia interface.

 

 

Firewire Connections

 

 

Common Applications
Firewire is frequently used by personal computers, high end digital cameras and camcorders, external hard drives and other digital video peripherals. IEEE 1394 (as well as USB) replaced parallel SCSI in many digital applications.  

Firewire v.s. USB
A USB network relies on a single host at the top of the "tree" to control the network. In a FireWire network, any capable node can control the network (conditions permitting).

USB networks use what is referred to as tiered-star topology, while FireWire networks use a tree topology.

USB 1.0, 1.1 and 2.0 peripherals cannot communicate with the host unless the host specifically requests communication (USB 3.0 will allow for such communication).
A FireWire device can theoretically communicate with any node at any time providing conditions allow.

USB runs with a 5 V power line, while Firewire can supply up to 30 V.

USB ports can provide from the typical 500mA[2.5 Watts] of current to USB 3.0 & USB On-The-Go's 1800mA[9.0W] (for dedicated battery charging, 1500mA[7.5W] Full Speed or 900mA[4.5W] High Speed), while FireWire can in theory supply up to 60 watts of power, although 10 to 20 watts is more typical.

These and other differences reflect the differing design goals of the two buses: USB was designed for simplicity and low cost, while FireWire was designed for high performance, particularly in time-sensitive applications such as audio and video. Although similar in theoretical maximum transfer rate, FireWire 400 has performance advantage over USB 2.0 Hi-Speed in real-use, especially in high-bandwidth use such as external hard-drives. The newer FireWire 800 standard being twice as fast as FireWire 400 outperforms USB 2.0 Hi-Speed both theoretically and practically. The chipset and drivers used to implement USB and Firewire have a crucial impact on how much of the bandwidth prescribed by the specification is achieved in the real world, along with compatibility with peripherals.

How to choose the right Firewire Cable for your application:
Be sure to check your equipment and hardware to determine the exact connections you have as that will always dictate the configuration of the cable you need. As with other digital cables, distance will be limited for Firewire cables (for now). Keep in mind the medium for transferring this digital data is still over analog copper cabling cable so construction will still play a role in final performance. As always, look for a well made, well shielded, cables from a reputable source at a fair market price. Since USB cable distances are limited, standard grade Firewire cables are all that are needed for everyday use. Do not waste money on fancy gold connectors or braided jackets as they provide no tangible performance benefit. Avoid retail brands that charge exorbitant prices. For more about overall cable construction, please click here.

Related Products: Firewire Cables, Firewire Hubs, USB Cables, USB Hubs, HDMI Cables