Study Unit 4 - Chapter Four Making Connections Flashcards
Introduction
Introduction
* Connecting peripheral devices to a computer has, in the
past, been a fairly challenging task
* Newer interfaces have made this task much easier
* Let’s examine the interface between a computer and a
device
– This interface occurs primarily at the physical layer
Interfacing a Computer to
Peripheral Devices
Interfacing a Computer to
Peripheral Devices
* The connection to a peripheral is often called the interface
* The process of providing all the proper interconnections
between a computer and a peripheral is called interfacing
Characteristics of Interface Standards
* There are essentially two types of standards
Characteristics of Interface Standards
* There are essentially two types of standards
– Official standards
* Created by standards-making organizations such as ITU (International
Telecommunications Union), IEEE (Institute for Electrical and Electronics
Engineers), (now defunct) EIA (Electronic Industries Association), ISO
(International Organization for Standardization), and ANSI (American
National Standards Institute)
– De facto standards
* Created by other groups that are not official standards but because of
their widespread use, become “almost” standards
Characteristics of Interface
Standards (continued)
* There are four possible components to an interface standard:
Electrical component: deals with voltages, line capacitance, and other
electrical characteristics
– Mechanical component: deals with items such as the connector or
plug description
– Functional component: describes the function of each pin or circuit
that is used in a particular interface
– Procedural component: describes how the particular circuits are used
to perform an operation
Two Important Interface Standards
* In order to better understand the four components of an
interface, let’s examine two interface standards
Two Important Interface Standards
* In order to better understand the four components of an
interface, let’s examine two interface standards
– EIA-232F – an older standard originally designed to connect a
modem to a computer
– USB (Universal Serial Bus) – a newer standard that is much more
powerful than EIA-232F
An Early Standard: EIA-232F
* Originally named RS-232 but has gone through many
revisions
* All four components are defined in the EIA-232F standard
An Early Standard: EIA-232F
* Originally named RS-232 but has gone through many
revisions
* All four components are defined in the EIA-232F standard:
– Electrical
– Mechanical (DB-25 connector and DB-9 connector)
– Functional
– Procedural
An Early Standard: EIA-232F
An Early Standard: EIA-232F
* EIA-232F also used the definitions DTE and DCE
– An example of a DTE, or data terminating equipment, is a computer
– An example of a DCE, or data circuit-terminating equipment, is some
form of modem
What is meant by duplexity?
* EIA-232F defines a full-duplex connection. What does this
mean?
What is meant by duplexity?
* EIA-232F defines a full-duplex connection. What does this
mean?
* A full-duplex connection transmits data in both directions and
at the same time
* A half-duplex connection transmits data in both directions but
in only one direction at a time
* A simplex connection can transmit data in only one direction
* Can you think of a modern example of each?
Universal Serial Bus (USB)
Universal Serial Bus (USB)
* The USB interface is a modern standard for interconnecting
a wide range of peripheral devices to computers
* Supports plug and play
* Can daisy-chain multiple devices
* USB 2.0 can support 480 Mbps (USB 1.0 is only 12 Mbps)
* USB 3.0 can support 4.8 Gbps
Universal Serial Bus (USB) (continued)
Universal Serial Bus (USB) (continued)
* The USB interface defines all four components
* The electrical component defines two wires VBUS and
Ground to carry a 5-volt signal, while the D+ and D- wires
carry the data and signaling information
* The mechanical component precisely defines the size of four
different connectors and uses only four wires (the metal shell
counts as one more connector)
Universal Serial Bus (USB) (continued)
Universal Serial Bus (USB) (continued)
* The functional and procedural components are fairly complex
but are based on the polled bus
* The computer takes turns asking each peripheral if it has
anything to send
* More on polling near the end of this chapter
FireWire
FireWire
* Low-cost digital interface
* Capable of supporting transfer speeds of up to 800 Mbps
* Hot pluggable
* Supports two types of data connections:
– Asynchronous connection
– Isochronous connection
Thunderbolt
Thunderbolt
* Digital interface currently found on Apple products
* Capable of supporting transfer speeds of up to 10 Gbps
* Uses same connector as existing Mini DisplayPort and
similar protocol as PCI Express
* Can daisy-chain devices and may get even faster with later
versions
SCSI and iSCSI
SCSI and iSCSI
* SCSI (Small Computer System Interface)
– A technique for interfacing a computer to high-speed devices such as
hard disk drives, tape drives, CDs, and DVDs
– Designed to support devices of a more permanent nature
* SCSI is a systems interface
– Need SCSI adapter
* iSCSI (Internet SCSI)
– A technique for interfacing disk storage to a computer via the Internet
InfiniBand and Fibre Channel
InfiniBand and Fibre Channel
* InfiniBand – a serial connection or bus that can carry multiple
channels of data at the same time
– Can support data transfer speeds of 2.5 billion bits (2.5 gigabits) per
second and address thousands of devices, using both copper wire
and fiber-optic cables
– A network of high-speed links and switches
* Fibre Channel – also a serial, high-speed network that
connects a computer to multiple input/output devices
– Supports data transfer rates up to billions of bits per second, but can
support the interconnection of up to 126 devices only
