IEEE 1394 invades the industrial realm

NASA Tech Briefs, Jul 2000

The high-performance serial bus lifts bandwidth and simplifies connectivity.

Its official name is IEEE 1394. It is also called FireWire^sup (R)^ by Apple and i.LINK^sup (R)^ by Sony, which has licensed this name to several other companies. It was created in the late 1980s as a digital technology designed to satisfy the ever-increasing demand for communications bandwidth for video. It was also designed to simplify and reduce the number of cables and connectors between devices. Simple one-cable connectivity has become a necessity brought about by miniaturization and increasing device functionality as ports have been reduced in size and number.

The IEEE 1394 high-performance serial bus has already found its way into consumer products and one day probably will link every digital appliance in the house: TV, DVR, camcorder, high-fidelity stereo, computers, and peripherals. Now it is poised to make the same impact on the industrial/scientific imaging world.

Guaranteed Bandwidth, Guaranteed Delivery

IEEE 1394 offers high-speed, bidirectional transfer of high volume digital data. It moves up to 400 Megabits/second of data, for applications requiring guaranteed bandwidth (isochronous mode), such as the delivery of video streaming images in real time, or guaranteed delivery (asynchronous mode) for the transfer of content-critical commands and file transfers that are not time-sensitive. Data transfer speeds are expected to double this year, with a top rate of up to 800 Megabits/second. Rates of up to 1200 Megabits/second are anticipated for next year.

IEEE 1394 is flexible and can be used with "tree" or "star" network topologies, connecting multiple devices together in a dynamic unsupervised network. Devices can be linked by low-cost serial cable with inexpensive four- or six-pin connectors. IEEE 1394 allows for cable lengths up to 14.8 feet and up to 236.1 feet between devices. Up to 16 hops are allowed between any two devices, and up to 63 devices can share the same bus. A single network can accommodate up to 1024 buses and 64,512 devices.

IEEE 1394 enables dynamic unsupervised bus management by facilitating automatic nonmanual bus configuration and reconfiguration. This includes automatic address selection and hot connect/disconnect of devices without loss of data. If a device is added or removed from the network, there is no need for the system to reboot, and there is no need for ID switches. Communications within the network are peer to peer; there is no need for a computer, just a bus manager on the network. The network can handle multiple CPUs and such devices as cameras, printers, CDROM drives, hard drives, and other storage devices, greatly enhancing flexibility and ease of maintenance.

Speed plus Bandwidth

IEEE 1394 supports bidirectional data transmission at speeds of 100, 200, or 400 Mb/s (megabits/second), or approximately 10, 20, and 40 MB/s (Megabytes/second). Future planned transmission rates are 800 Mb/s (80 MB/sec) and 1.6 Gb/s (160 MB/s). By contrast, the common USB (universal serial bus) 1.0 interface only supports about 1.2 Mb/s. The SCSI (small computer system instruction) interface supports a small number of devices on the network while providing data transfer at 5 to 30 MB/s with large, expensive cables and connectors. Traditional video interfaces such as SDTI and RS422 support rates of approximately 25 MB/s and 1 to 16 MB/s respectively. SDTI and RS-422 also have the disadvantage of utilizing large, expensive connectors, and have limited networking capability. On the horizon are interfaces such as USB 2.x and Channel Link'". USB 2.x has limited networking capability and is computer-concentric, supporting speeds of approximately 30 MB/s. Channel Link, the fastest of these interfaces, supports 100 MB/s, but has no networking capability-it is strictly a point-to-point connectionand it requires four or five pairs of cables and connectors to link devices. Channel Link is a very specialized connection, one usually used in video applications.

The bottom line is that the IEEE 1394 interface supports more bandwidth, flexibility, reduced cabling, and lower costs than anything on the market today.

In 1995, 1394 was officially adopted by the Institute of Electrical and Electronics Engineers (IEEE) as a highspeed digital interface among audio/ video products, personal computers, and peripheral devices. It has also been adopted as a standard by the Digital Audio Video Council (DAVIC) for home networks. The Digital Video Broadcasters (DVB) and the Electronics Industry Association (EIA) have also adopted 1394 for digital broadcast receivers. In addition, IEEE 1394 is gaining rapid acceptance in the industrial and scientific arenas.

Sony and IEEE 1394

Because Sony saw IEEE 1394's potential immediately, the company joined the IEEE 1394 Trade Association in 1994. There are many working groups within the trade association that are developing standards for digital cameras for industrial markets. For example, DCAM^sup (R)^ Version 1.2 defines specifications on how 1394 cameras should work. It has evolved to support new triggering, partial scan interfaces, a wider range of operating systems, and connectors.