IEEE 1394, USB, or both?

Over the years, the computer industry has seen various buses come and go. In the late '80s, IBM announced its line of PS/2 computers that came with the proprietary Microchannel bus. Compaq and other PC manufacturers counterattacked with the Enhanced Industry Standard Architecture (EISA) bus. The latter, an open bus, prevailed. But even it succumbed to the more-popular ISA bus.

Some writers who cover the computer industry feel the time has come for another battle, this time between groups that prefer either the IEEE 1394 or the Universal Serial Bus (USB). Actually, plenty of room exists for both. (The 1394 bus is now 1394b, and the USB is now called USB 2.0.)

The 1394 bus, Apple's Firewire, was meant to serve high-speed peripherals in a peer-to-peer network. Devices on the bus can arbitrate to control the bus and initiate transfers of data at rates as high as 400 Mbps. Today's trends in 1394 applications seem to indicate the bus will find most use in home-entertainment systems. In fact, the IEEE 1394 standard includes specifications for audio- and video-transfer modes. But if people wish to employ the bus in a T&M application, they can.

On the other hand, the USB was developed to replace with a single connection the multiple serial, parallel, keyboard, and mouse ports on a PC. Users can get confused by all the connections on the back of a PC, so manufacturers decided to offer one simple connector. The USB relies on a central controller—usually the PC—to manage all external devices that would communicate over the 480-Mbps serial bus. USB ports usually come free with a PC, but you have to buy and add 1394 ports as you need them.

Today, both the 1394 bus and the USB find use in T&M applications, and both buses coexist in a PC. Sony sells cameras that provide a 1394 connection, and Analogic offers an arbitrary waveform generator that comes with a 1394 interface. The USB community includes IOtech, National Instruments, Data Translation, and JTAG Technologies. Each company chose a specific bus for a variety of reasons, including data rates, the need for a controlling host, available software drivers, supported protocols, and so on.

The RS-232 serial bus, the IEEE 488 instrumentation bus, and the Ethernet have coexisted peacefully for a long time—and will continue to find use in T&M applications for many years. The T&M market should welcome without prejudice adherents of the IEEE 1394 bus and the USB. In the end, customers will determine what sells and what doesn't.