IEEE 1394 (FireWire) Interface

Before you start

Objectives: Learn what is FireWire, about different FireWire connectors and about different FireWire versions.

Prerequisites: no prerequisites.

Key terms: device, connector, bus, data, megabits, version, transfer, cable, wire, length, interface, pin

Description of FireWire

FireWire can transfer data at 400 megabits per seconds. It’s can be used by external hard drives, external digital cameras, external CD and DVD drives, digital video cameras, etc. When FireWire was first introduced, USB only ran at 12 megabits per second. At that time FireWire seemed like the better solution. Now that USB 2.0 runs at 480 megabits per second, FireWire is loosing its popularity. It’s not as widely implemented as USB. It uses a serial bus using twisted-pair wiring for data transport. It supports cables up to 4,5 meters in length, and let’s us connect 63 different devices on one IEEE 1394 bus. Devices can be bus powered or self powered.


FireWire uses three different types of connectors. The first type is a large six wire connector that uses a plug and socket shown on the picture.

 6 pin firewire

Image 319.1 – 6 pin FireWire Connector

This connector has a bevel on the edges to keep us from inserting this cable the wrong way. IEEE 1394 cables with six wires are self-powered. There’s also a smaller four wire connector that is shown on the picture. We will probably see this connector on our PC.

 4 pin firewire

Image 319.2 – 4 Pin FireWire Connector

It’s quite small and this is the connector that we’ll probably see on our devices. IEEE 1394 cables with four wires are not self-powered. We also have a nine pin connector which is a of a recent improvement to the IEEE-1394 technology. It is called FireWire 800 (or IEEE-1394b) and allows transfer of data at twice the speed of the original IEEE-1394 standard, or even more.

 9 pin firewire

Image 319.3 – 9 Pin FireWire Connector

Multiple Devices

Using FireWire we can connect multiple devices to the same bus. This way all devices are connected together to the same interface on the PC system. This is similar to USB, but the difference is that USB uses a tiered star topology, and with FireWire we daisy chain the devices. Daisy chain means that we connect one device to the interface card, then we connect that device to another device, and then that device to another device. The maximum number of hops (other devices) between any two devices is 16. All FireWire devices are self-configuring. When we plug the device in it automatically identifies itself to the operating system on the PC. The PC can then load the appropriate drivers to make the device available. Also, FireWire devices are also hot swappable. That means that we don’t have to shut down our PC when we plug or unplug FireWire devices. FireWire can also provide power to devices, but up to certain limits. It also supports peer-to-peer transfer. That means that we can transfer data between connected devices, without going trough the computer.

IEEE 1394 Versions

Version 1394 supports speeds of 100, 200 and 400 megabits per second. Maximum cable length for this version is 4.5 meters (15 feet).Version 1394.A clarifies and enhances the original standard. Version 1394.B supports speeds of 800, 1600, and 3200 megabits per second. Maximum cable length for this version is 100 meters (328 feet). Version 1394.3 supports peer-to-peer data transmission which means that some device can send data directly to another device, without computer involvement required.


IEEE 1394 can transfer data at 400 megabits per seconds, maximum cable length is 4.5 meters, and it let’s us connect 63 different devices on one bus. Devices can be bus powered or self powered. Connectors can be 4 wire, 6 wire and 9 wire connectors. When connecting multiple devices with FireWire, we daisy chain them. FireWire devices are hot swappable.