ppsx - MTI University
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Transcript ppsx - MTI University
Prof. Dr. M. H. Assal
A.S. 2/4/2014
The interfaces for attaching external devices to a computer
or
The doors through which information enters and leaves a
computer system. and leaves a computer system.
o PS/2 ports (Mouse, Keyboard)
o Serial ports (Mouse, modems, printers) 150 kbps
o Parallel ports (printers, scanners, external data drives) 1.2 mbps
o SCSI ports – Small Computer Systems Interface
(many internal and external devices) up to 320 mbps
o USB ports - Universal Serial Bus
(nearly everything) 1.5 - 12 - 480 - 4000 mbps
o Firewire Connections (imaging devices – digital camcorders,
scanners) 100-800 mbps
2
PS/2 Ports
Serial Port
SCSI
Parallel Port
USB
Firewire Ports
3
Fast
Reliable
Flexible
Inexpensive
Power-conserving
Supported by the operating system
4
Commonly known as the printer port
25 pin D-Type connector
It has 12 digital output pins, 5 digital input pins
Pins operate at the TTL voltage level i.e. 0 – 5V
Port identified by a base address in the computer I/O
memory space
5
9
pin D-Type connector
Pins operate at -25 to +25 voltage levels
Data transmitted as a bit sequence
Known as the EIA RS232C port or simply RS232
Maximum date rate of 19,600 bps
7
Serial
cables can be much longer than Parallel
cables
Serial suited for wireless transmission
8
Universal Serial Bus (USB) was designed in mid-1990s to
standardize the connection of computer peripherals to
computers.
It has become commonplace on other devices (such as
smartphones, PDAs and video game consoles).
USB has effectively replaced a variety of earlier interfaces, such
as serial and parallel ports.
USB is a likely solution any time you want to use a computer to
communicate with devices outside the computer
Device, male connector
Computer, female connector
Hub
9
Comparison
Interface
USB
# of Devices
(maximum)
Length
(max feet)
127
16 (or up to
96 ft. with 5
hubs)
Speed
(max. bps)
Ver. 1.0
1.5 M
Ver. 1.1
12 M
Ver. 2.0
480 M
Ver. 3.0
5G
Typical Use
(nearly everything)
Mouse, Keyboard,
Hard Drives, Mass Storage,
Network Adapters,
Audio, Camcorders
RS-232
2
50-100
20 K
(115K with some
hardware)
Modems, Mouse
Bar-Code Readers
Instrumentation
Parallel
2
10–30
8M
Printers
Scanners
IEEE-1394
(FireWire)
64
15
(Printer) Port
IEEE-1394a
400 M
IEEE-1394b
3.2 G
Digital Video (Camcorders)
Old iPod & iPhone
Mass Storage
10
USB Features
Flexible
Ease of use was a major design goal for USB, and the result is an interface that’s a pleasure to use for
many reasons: Windows automatically detects the peripheral and loads the appropriate software
driver.
There’s no need to locate and run a setup program or restart the system before using the peripheral.
One interface for many devices.
USB is versatile enough to be usable with many kinds of peripherals. Instead of having a different
connector type and supporting hardware for each peripheral, one interface serves many.
Speed
USB supports three bus speeds: high speed data transfer.
Reliability
The reliability of USB results from both the hardware design and the data-transfer protocols.
Low Cost
Low Power Consumption
12
It’s Not Perfect
Lack of Support for Legacy Hardware
Older (“legacy”) computers and peripherals don’t have USB ports. If you want to connect
a non-USB peripheral to a USB port, a solution is a converter that translates between USB
and the older interface .
Distance Limits
USB was designed as a desktop bus, with the expectation that peripherals would be
relatively close at hand. A cable segment can be as long as 5 meters.
You can increase the length of a USB link to as much as 30 meters by using cables that
link five hubs and a device, using 6 cable segments of 5 meters each.
Peer to Peer Communications
USB can’t talk to each other directly. All communications are to or from the host computer.
Other interfaces, such as IEEE-1394, allow direct peripheral- to-peripheral
communications.
13
USB 2.0
A big step in USB’s evolution was version 2.0.
Support for much faster transfers.
a 40-times increase was found to be feasible, for a bus speed of
480 Megabits per second.
USB 2.0 is backwards compatible with USB 1.1.
Version 2.0 peripherals can use the same connectors and cables
as 1.x peripherals.
14
USB 3.0
Released in November 2008
Also referred to as SuperSpeed USB
Speeds 10x faster than 2.0 (5 Gbps in controlled test environment)
Extensible – Designed to scale > 25Gbps
Optimized power efficiency
Backward compatible with USB 2.0
o USB 2.0 device will work with USB 3.0 host
o USB 3.0 device will work with USB 2.0 host
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USB 3.0 Connectors
Added pins for SuperSpeed USB
signals.
Compatibility for USB 2.0 connectors.
Different shapes of connectors are
provided to support the compatibility
with current (USB 1 & 2) devices.
16
USB
Multiple devices
support
Firewire
Single host can communicate with many
peripherals/devices
127
Peer to Peer
No Peer-to-Peer support
Cost
Relatively Cheap
64
Support Peer-to-Peer
model, where
peripherals can
communicate with
each other directly
Expensive
23