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FireWire/IEEE 1394 FAQs
This information presents and answers some of the most common questions about FireWire/IEEE 1394 cabling. Click the Shop link to access that section in the online catalog.
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- What is this FireWire/IEEE 1394 I’ve been hearing about?
- Who benefits from FireWire/IEEE1394?
- What makes up the IEEE 1394 cable?
- What’s significant about the connectors?
- What kind of distances or numbers of connections are possible?
- What is the IEEE 1394 architecture for A/V devices Windows 98 support?
- How about Windows 2000 support for storage, printers, and scanners?
IEEE 1394 is a serial protocol that runs at speeds ranging from 100 to 400 megabits per second (Mbps), depending upon the implementation. The 1394 Trade Association is working to deliver speeds in the future of 800 Mbps, 1 gigabits per second (Gbps), and 1.6 Gbps. IEEE 1394 provides a high-speed, Plug and Play-capable bus that eliminates the need for peripherals to have their own power supplies and provides support for isochronous data transfer. It is the bridge that brings PCs and consumer electronics together for example, a digital VCR can be used as a PC peripheral both for movie playback and for recording video streams that have been edited on the PC. Digital VCRs, DV camcorders, and digital satellite receivers are being shipped now with IEEE 1394 interfaces. Because of the very high data rates that IEEE 1394 can handle, it is ideal for consumer electronics audio/video (A/V) appliances, storage, printing, and high-resolution scanning, plus other portable devices.
Who benefits from FireWire/IEEE1394?
IEEE 1394 supports a modular PC architecture that benefits end users, who can take advantage of IEEE 1394 to upgrade or expand system capabilities to include new consumer electronics appliances and PC peripherals. Manufacturers benefit from being able to take advantage of a single industry standard for peripheral interconnectivity.
What makes up the IEEE 1394 cable?
The IEEE 1394 cable contains six copper wires: two wires carry power and the other four wires are grouped into two twisted-wire signal pairs. Each twisted pair is shielded as is the entire cable.
The power wires carry between 8 to 40 VDC at up to 1.5 amps, and are used to:
- maintain a device's physical layer continuity when the device is powered down or malfunctions - very important for a serial topology
- provide power for devices connected to the bus
What’s significant about the connectors?
The cable connector is constructed such that the electrical contact is made inside the structure of the connector, thus preventing any shock to the user or contamination of the contacts by the user's hands. This small and flexible connector is very durable and easy to use even in situations where the user must blindly insert it into the back of a device. There is no cable terminator required or addressing ID to be set. A second cable design has emerged that is smaller and lighter than this cable. Currently used on the Sony Digital Video Handycams, this four-wire cable does not contain the power wires.
What kind of distances or numbers of connections are possible?
Up to 63 IEEE 1394 devices may be connected to a bus segment. Each device may be up to 4.5 meters apart with longer distances possible with repeater hardware. There is current design activity to extend this distance to 25 meters. Over 1000 bus segments may be connected by bridges, thereby providing a large growth potential. An IEEE 1394 device may be added to or removed from the bus at any time - even with the bus in full operation. Upon altering the bus configuration, there is an automatic reassignment of node addresses. This plug and play feature eliminates the need for address switches or other user intervention when reconfiguring the bus.
What is the IEEE 1394 architecture for A/V devices Windows 98 support?
In Windows 98, the Microsoft IEEE 1394 driver stack supports host adapaters compliant with the Open Host Controller Interface (OHCI or OpenHCI) standard. Windows 98 also supports the Adaptec and PCILynx adapter. Windows 2000 supports only OHCI-compliant adapters. Microsoft is providing base-level support for IEEE 1394 A/V devices in Windows 98 and in Window 2000 through the WDM Stream class, which supports components such as DVD decoders, MPEG decoders, video decoders, tuners, and audio codecs. The WDM Stream class supports a uniform model for standard and custom data types, following the kernel streaming conventions described in the current version of the Windows 2000 DDK to support data transfer between kernel drivers without requiring a transition to user mode. Digital video (DV) capture and editing applications communicate with the device driver layer through the A/V framework and the DirectShow DV and MPEG-2 codecs.
How about Windows 2000 support for storage, printers, and scanners?
Storage support is available in Windows 2000 through the Serial Bus Protocol (SBP-2) port driver. Small Computer System Interface (SCSI) class drivers can use SBP-2 as a passthrough to talk to IEEE 1394 devices. For example, an IEEE 1394 scanner is supported by SBP-2 and the existing SCSI driver architecture and stack. One advantage of SBP-2 is that it can encapsulate any command set. Support for IEEE 1394 hard disks, CD-ROM drives, DVD drives, printers, and scanners is implemented through the SBP-2 protocol on Windows 2000. As shown in Figure 2, the hardware and bus driver layers are nearly identical to the architecture for A/V as shown in Figure 1. Support for storage, printers, and scanners is through the SBP-2 class driver, which communicates through the SBP-2 port driver. Printers provide a good example of IEEE 1394 support available in Windows 2000. To implement IEEE 1394 on a printer, the vendor only needs to:
- Implement the SBP-2 protocol on the printer.
- Use the SCSI printer command set (a minimal set of commands).
Note for Windows 98:IEEE 1394 storage devices are supported in Windows 98 Second Edition, but IEEE 1394 printers and scanners are not supported in this release.
