|
|
|
1394
FireWire Overview |
| |
IEEE 1394
provides the common rules of operation required to create this
in an orderly fashion. The technology is constructed -- and
can be envisioned -- in layers. Generally, these layers include
the cable and connectors mechanical physical layer; the electrical
physical layer, in which signaling specifications and networking
rules are detailed; the link layer, which formats or manipulates
transported data for easier use by the application; and the
protocol/application layer, which includes higher level system
guidelines/ interfaces that bring the data, the end system design,
and the application together. Figure 1 illustrates the layers.
To illustrate the 1394 ‘map,’ consider a national highway system.
The cable and connector represent the road and its traffic lanes.
The rules of the road are reflected in the physical and link
layers, while the target applications are represented by various
users of the road -- commercial goods transporters, family vehicles,
nationwide commercial busing transportation, military equipment
convoys, and others. It is a complex web governed by basic regulations
and a set of mutual understandings that keep traffic ‘moving’
reliably and efficiently.
Like the highway driver, 1394 applications share a subset of
rules, yet there are elements of the standards and application
specifications for which they are unconcerned or unaware. Car
drivers don’t exit for truck weigh stations, for example, and
bridge clearances are designed so that military vehicles can
safely traverse intersections (a fact some car drivers may not
realize). Cars, trucks, and military equipment use the same
highway, are guided by speed limits, and use identical passing
guidelines. This is essentially the way the 1394 protocol stack
operates. It is efficient, and does not demand that all elements
understand all the activity that takes place at the same time
|
| |
| |
|
