Information Technology Reference
In-Depth Information
Figure 9.4
IEEE-1394 cable and connectors
9.4 Exercises
9.4.1
How many USB ports are available from the host controller on a PC (PIIX3/4):
(a)
1
(b)
2
(c)
4
(d)
8
9.4.2
Discuss the advantages of USB connected devices over:
(i)
ISA devices
(ii)
PCI devices
(iii)
Serial/parallel port connected devices
9.4.3
Outline the main difference between isochronous and asynchronous data traffic. In
which applications is it isochronous.
9.4.4
Outline the main types of data transfer on the USB port.
9.4.5
By searching the Internet or a computer catalogue, locate some USB connected
devices.
9.5
Notes from the author
Congratulations go to the USB port. It was the first truly generic, easy-to-use, connection
bus for the PC that has mechanisms for non-real-time (such as printer data) and real-time
data (such as video, audio and speech). It allows for the easy addition and removal of de-
vices from the system, and it also supports hot plugging (adding or removing a device while
the computer is on). Microsoft first supported USB in Windows 95 OSR2, and it has since
become one of the most used ports, for devices such as video cameras, CD-ROM drives,
printers, digital speakers, monitors, and so on. The only problem with USB is that it only
gives a data throughput of 12 Mbps, and thus cannot be used for high-speed devices. Possi-
bly, over time, this rate may be increased, or other faster busses, such as Firewire could be
used for high-speed applications, such as Fast Ethernet, multimedia communications, hard
disk interfaces, and so on.
The IEEE-1394 specification (or i.LINK) is now being used on some systems (especially
in notebooks). Its adoption as a standard interface device will depend on whether new stan-
dard for the USB specification increase the transfer bit rate to support, at least, 100Mbps.
When the USB port can do this, there will be a lesser need for IEEE-1394.
