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IEEE 1394

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IEEE 1394 is a technical standard for a high-speed serial bus.

FireWire symbol
FireWire symbol

A serial bus moves information one bit at a time. This is different from a parallel bus, which uses many connections at once. Parallel buses are often heavier and more expensive to build. IEEE 1394 allows for high-speed communications and real-time data transfer. This makes it excellent for moving large amounts of information quickly. Apple calls this technology FireWire. Other companies use different names like i.LINK or Lynx.

FireWire cables
FireWire cables

This system manages data using two specific methods. The first is isochronous transfer, which provides a guaranteed path for data. This is vital for video or audio that must stay steady without stopping. To ensure this, the system reserves 80% of the bus for isochronous cycles. The remaining 20% is used for asynchronous data. Asynchronous data does not require a constant, guaranteed stream.

Image-FireWire-46 Connector Pinout
Image-FireWire-46 Connector Pinout

The system also allows peer-to-peer communication. This means a scanner can talk to a printer directly. They do not need to use the computer's CPU or system memory to do this.

To keep everything organized, the devices use a tree topology.

Firewire PCI VIA VT6306
Firewire PCI VIA VT6306

This means devices connect in a branching structure rather than a simple line. You can connect up to 63 different peripherals in this tree or daisy-chain setup. Each device has a unique self-ID to tell it apart from others. One device is elected as the root node. The root node always has the highest ID in the group. After a bus reset, the devices assign these IDs by traversing the tree in a specific order.

Managing who speaks and when is a process called arbitration.

Each arbitration round lasts about 125 microseconds. During this time, the root node sends a cycle start packet. Any device that needs to send data will respond. The device closest to the root node wins the right to transmit first. After one device finishes, the others take turns. This cycle repeats until the 125-microsecond window is over. This ensures that isochronous transfers always get their priority.

Apple began developing this technology in 1986. They wanted a serial replacement for the parallel SCSI bus. They worked with the IEEE P1394 Working Group to finish the project. Many companies contributed to the development through their engineering and patents. Sony contributed 102 patents to the project. Apple contributed 58 patents, while Panasonic provided 46 and Philips provided 43. Other companies like Toshiba and Canon also provided engineering help. The standard was officially completed in January 1995.

There have been several versions of the standard over time. The original IEEE 1394-1995 is known as FireWire 400. It supports speeds called S100, S200, and S400.

The 6-conductor version can supply up to 45 watts of power. This allows devices to work without a separate power supply. The 1394a amendment arrived in 2000 to improve efficiency. It added a power-saving mode and faster bus reconfiguration. Later, the 1394b-2002 standard introduced FireWire 800. This version uses a 9-pin connector and allows for full-duplex communication.

While FireWire was very popular, it has mostly been phased out. Most manufacturers stopped using it in the 2010s. Apple began moving toward Thunderbolt in 2011.

FireWire 800 port
FireWire 800 port

Thunderbolt eventually became the standard for Apple computers. However, IEEE 1394 was very significant for professional work. It was used in industrial machine vision and professional audio systems. It was often preferred over USB 2.0 because it had higher sustained data rates. Even though it is older, it paved the way for how modern devices connect and share power.

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🖼️ Images & Media (10)
File:FireWire symbol.svg
FireWire symbol.svg
File:Image-FireWire-46 Connector Pinout.svg
Image-FireWire-46 Connector Pinout.svg
File:FireWire800 Stecker.jpeg
FireWire800 Stecker.jpeg
File:Ethernet plug grey.svg
Ethernet plug grey.svg
File:FireWire cables.jpg
FireWire cables.jpg
File:Firewire PCI VIA VT6306.jpg
Firewire PCI VIA VT6306.jpg
File:CreativeTools.se - PackshotCreator - ExpressCard (5987600166) (cropped).jpg
CreativeTools.se - PackshotCreator -...
File:CreativeTools.se - PackshotCreator - Firewire adapter (5078491584) (cropped).jpg
CreativeTools.se - PackshotCreator -...
File:FireWire 800 port.jpg
FireWire 800 port.jpg
File:Firewire800.jpg
Firewire800.jpg
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