Transcript ppsx - MTI University

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Prof. Dr. M. H. Assal
A.S. 2/4/2014
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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
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PS/2 Ports
Serial Port
SCSI
Parallel Port
USB
Firewire Ports
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Fast
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Reliable
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Flexible
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Inexpensive
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Power-conserving
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Supported by the operating system
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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
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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
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 Serial
cables can be much longer than Parallel
cables
 Serial suited for wireless transmission
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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
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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
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50-100
20 K
(115K with some
hardware)
Modems, Mouse
Bar-Code Readers
Instrumentation
Parallel
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10–30
8M
Printers
Scanners
IEEE-1394
(FireWire)
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15
(Printer) Port
IEEE-1394a
400 M
IEEE-1394b
3.2 G
Digital Video (Camcorders)
Old iPod & iPhone
Mass Storage
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USB Features
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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.
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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.
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Speed
USB supports three bus speeds: high speed data transfer.
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Reliability
The reliability of USB results from both the hardware design and the data-transfer protocols.
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Low Cost
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Low Power Consumption
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It’s Not Perfect
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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.
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USB 2.0
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A big step in USB’s evolution was version 2.0.
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Support for much faster transfers.
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a 40-times increase was found to be feasible, for a bus speed of
480 Megabits per second.
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USB 2.0 is backwards compatible with USB 1.1.
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Version 2.0 peripherals can use the same connectors and cables
as 1.x peripherals.
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USB 3.0
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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
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Added pins for SuperSpeed USB
signals.
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Compatibility for USB 2.0 connectors.
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Different shapes of connectors are
provided to support the compatibility
with current (USB 1 & 2) devices.
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USB
Multiple devices
support
Firewire
Single host can communicate with many
peripherals/devices
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Peer to Peer
No Peer-to-Peer support
Cost
Relatively Cheap
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Support Peer-to-Peer
model, where
peripherals can
communicate with
each other directly
Expensive
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