Hardware Reference
In-Depth Information
Figure 14.15. IEEE 1394a port connectors.
The 1394 bus was derived from the FireWire bus originally developed by Apple and Texas
Instruments. The 1394a uses a simple six-wire cable with two differential pairs of clock and data
lines, plus two power lines; the four-wire cable/connector shown in Figure 14.15 is used with self-
powered devices, such as DV camcorders. Just as with USB, 1394 is fully PnP, including the
capability for hot-plugging (insertion and removal of components without powering down).
Built on a daisy-chained and branched topology, 1394 allows up to 63 nodes, with a chain of up to 16
devices on each node. If this is not enough, the standard also calls for up to 1,023 bridged buses,
which can interconnect more than 64,000 nodes! Additionally, as with SCSI, 1394 can support
devices with various data rates on the same bus. Most 1394 adapters have three nodes, each of which
can support 16 devices in a daisy-chain arrangement. Some 1394 adapters also support internal 1394
devices.
The types of devices that can be connected to the PC via 1394 include mainly video cameras, editing
equipment, and external drives. The 1394 bus appears in many desktop and laptop computers as a
supplement to other external high-speed buses, such as USB and eSATA.
Chipsets enabling PC Card/CardBus and ExpressCard adapters for the 1394 bus are available from a
number of manufacturers, including some models that support both 1394 and other port types in a
single slot. Microsoft has included support for 1394a in Windows 98SE and later. Windows 7 and
later have updated that support to include 1394b. The most popular devices that utilize 1394 are
camcorders, digital video recorders, and external storage drives. Sony was among the first to release
1394 devices, however in typical Sony fashion, Sony doesn't call it 1394 or FireWire; it has created
its own designation (i.LINK) instead. Just remember that whether it is called 1394, FireWire, or
i.LINK, it is basically the same thing. Digital video (DV) products and storage drives using 1394 are
available from many other companies.
1394b Technical Details
IEEE 1394b is the second generation of the 1394 standard, with the first products (high-performance
external hard drives) introduced in January 2003. IEEE 1394b uses one of two 9-pin cables and
connectors, along with 8b/10b encoding to support speeds of 800Mbps-3,200Mbps with copper or
fiber-optic cabling. In addition to supporting faster transfer rates, 1394b has other new features,
including the following:
 
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