Download Buses and Interfaces - Mahanakorn University of Technology

BUSES AND INTERCONNECTS
CPU-Memory-I/O Architecture
Memory
I/O
modul
e
CPU
“CPU bus”
or
“System bus”
“Bus interface”
“I/O bus”
I/O
device
I/O Buses and Interfaces
 There are many “standards” for I/O buses and
interfaces
 Standards allow “open architectures”
 Many vendors can provide peripheral (I/O) devices
for many different systems
 Most systems support several I/O buses and
I/O interfaces
Examples
 Expansion buses or “slots”
 Disk interfaces
 External buses
 Communications interfaces
Expansion Buses
 These are “slots” on the motherboard
 Examples









ISA – Industry Standard Architecture
PCI – Personal Component Interconnect
EISA – Extended ISA
SIMM – Single Inline Memory Module
DIMM – Dual Inline Memory Module
MCA – Micro-Channel Architecture
AGP – Accelerated Graphics Port
VESA – Video Electronics Standards Association
PCMCIA – Personal Computer Memory Card
International Association (not just memory!)
3 ISA
slots
5 PCI
slots
Pentium CPU
6 SIMM
slots
2 DIMM
slots
Examples
 Expansion buses or “slots”
 Disk interfaces
 External buses
 Communications buses
Disk Interfaces
 Examples
 ATA – AT Attachment (named after IBM PC-AT)
 IDE – Integrated Drive Electronics (same as ATA)
 Enhanced IDE
 Encompasses several older standards (ST-506/ST-412, IDE,
ESDI, ATA-2, ATA-3, ATA-4)
 Floppy disk
 SCSI – Small Computer Systems Interface
 ESDI – Enhanced Small Device Interface (mid-80s,
obsolete)
 PCMCIA - Personal Computer Memory Card
International Association (not just memory!)
Examples
 Expansion buses or “slots”
 Disk interfaces
 External buses
 Communications buses
External Buses
 Examples
 Parallel – sometimes called LPT (“line printer”)
 Serial – typically RS232C (sometimes RS422)
 PS/2 – for keyboards and mice
 USB – Universal Serial Bus
 IrDA – Infrared Device Attachment
 FireWire – new, very high speed, developed by
IEEE
Examples
 Expansion buses or “slots”
 Disk interfaces
 External buses
 Communications buses
Communications Buses
 For connecting systems to systems
 Parallel/LPT
 special purpose, e.g., using special software
(Laplink) to transfer data between systems
 Serial/RS232C
 To connect a system to a voice-grade modem
 Ethernet
 To connect a system to a high-speed network
A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
ISA (1 of 3)
 Industry Standard Architecture
 pronounced “eye-es-eh”
 History
 Originally introduced in the IBM PC (1981) as an 8 bit
expansion slot
 Runs at 8.3 MHz with data rate of 7.9 Mbytes/s
 16-bit version introduced with the IBM PC/AT
 Runs at 15.9 MHz with data rate of 15.9 Mbytes/s (?)
 Sometimes just called the “AT bus”
 Today, all ISA slots are 16 bit
 Configuration
 Parallel, multi-drop
p. 180
ISA (2 of 3)
 Used for…
 Just about any peripheral (sound cards, disk drives, etc.)
 PnP ISA
 In 1993, Intel and Microsoft introduced “PnP ISA”, for plug-
and-play ISA
 Allows the operating system to configure expansion boards
automatically
 Form factor




Large connector in two segments
Smaller segment is the 8-bit interface (36 signals)
Larger segment is for the 16-bit expansion (62 signals)
8-bit cards only use the smaller segment
ISA (3 of 3)
 Advancements
 EISA
 Extended ISA
 Design by nine IBM competitors (AST, Compaq, Epson, HP,
NEC, Olivetti, Tandy, WYSE, Zenith)
 Intended to compete with IBM’s MCA
 EISA is hardware compatible with ISA
 MCA
 Micro Channel Architecture
 Introduced by IBM in 1987 as a replacement for the AT/ISA bus
 EISA and MCA have not been successful!
A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
PCI
 Peripheral Component Interconnect
 Also called “Local Bus”
 History




Developed by Intel (1993)
Very successful, widely used
Much faster than ISA
Gradually replacing ISA
 Configuration
 Parallel, multi-drop
PCI
 Used for…
 Just about any peripheral
 Can support multiple high-performance devices
 Graphics, full-motion video, SCSI, local area networks,
etc.
 Specifications




64-bit bus capability
Usually implemented as a 32-bit bus
Runs at 33 MHz or 66 MHz
At 33 MHz and a 32-bit bus, data rate is 133 Mbytes/s
PCI Local Bus Specification:
 PCI version 1.0 was developed by Intel in 1991 but not released by a
Standards body.
 PCI revision 2.0; released in 1993; 32-bit, 33MHz bus.
 PCI revision 2.1; released in 1995; 32-bit, 33MHz / 64-bit, 66MHz,
Universal PCI for 3.3v or 5v cards
 PCI revision 2.2; released 1998; minor clarifications / enhancements.
 PCI revision 2.3; released in 2002; removed 5v only cards
 PCI revision 3.0; released in 20xx; removed 5 volt interfaces
altogether.
PCI-X: The latest version 64 bits
at: PCI-X 66, PCI-X 133, PCI-X 266
and PCI-X 533 [4.3GBps]
PCI express
 PCI Express is the new serial bus addition to the PCI series of
specifications. How ever the electrical and mechanical interface for
PCI Express is not compatible with the PCI bus interface. This is a
serial bus which uses two low-voltage differential LVDS pairs, at
2.5Gb/s in each direction [one transmit, and one receive pair]. A PCI
Express link is comprised of these two unidirectional differential
pairs each operating at 2.5Gbps to achieve a basic over all
throughput of 5Gbps [before accounting for over-head].
PCI Express Protocol
 The frame format for PCIe is shown in the graphic below. The frame
is made up of a 1-byte Start-of-Frame, 2-byte Sequence Number, 16
or 20-byte Header, 0 to 4096-byte Data field, 0 to 4-byte ECRC field,
4-byte LCRC, and 1-byte End-of Frame. The smaller the number of
bits transferred in the data field the greater the over-head becomes.
A zero byte data field results in a 100 percent over-head, because no
data was transferred.
PCI Express Throughput
A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
AGP
 Accelerated Graphics Port
 History
 First appeared on Pentium II boards
 Developed just for graphics (especially 3D graphics)
 Configuration
 Parallel, point-to-point (only one AGP port / system)
 Specifications
 Data rates up to 532 Mbytes/s (that’s 4x PCI!)
Available Versions
AGP 1x, using a 32-bit channel operating at 66 MHz resulting
in a maximum data rate of 266 megabytes per second
(MB/s); 3.3 V signaling.
AGP 2x, using a 32-bit channel operating at 66 MHz double
pumped to an effective 133 MHz resulting in a maximum data
rate of 533 MB/s; signaling voltages the same as AGP 1x.
AGP 4x, using a 32-bit channel operating at 66 MHz quad
pumped to an effective 266 MHz resulting in a maximum
data rate of 1066 MB/s (1 GB/s); 1.5 V signaling.
AGP 8x, using a 32-bit channel operating at 66 MHz,
strobing eight times per clock, delivering an effective 533
MHz resulting in a maximum data rate of 2133 MB/s (2 GB/s);
0.8 V signaling.
Identifying ISA, PCI, & AGP
slots
 Here’s an image to help in identifying slots
Back of
computer
AGP slot
PCI slot
ISA slot
A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
Serial Interfaces
 On PCs, a “serial interface” implies a “COM
port”, or “communications port”
 COM1, COM2, COM3, etc.
 COM ports conform to the RS-232C interface
standard, so…
RS-232C
 History
 Well-established standard, developed by the EIA
(Electronics Industry Association) in 1960s
 Originally intended as an electrical specification to
connect computer terminals to modems
 Defines the interface between a DTE and a DCE




DTE = Data Terminal Equipment (terminal)
DCE = Data Communications Equipment (modem)
A “modem” is sometimes called a “data set”
A “terminal” is anything at the “terminus” of the
connection
 VDT (video display terminal), computer, printer, etc.
“Traditional” Configuration
DTE
DCE
RS-232C
DCE
Telephone
network
DTE
RS-232C
RS-232C Specifications
 Data rate
 Maximum specified data rate is 20 Kbits/s with a
maximum cable length of 15 meters
 However…
 It is common to “push” an RS-232C interface to higher data
rates
 Data rates to 1 Mbit/s can be achieved (with short cables!)
 Configuration
 Serial, point-to-point
Serial Data Transmission
 Two modes
 Asynchronous
 The transmitting and receiving devices are not
synchronized
 A clock signal is not transmitted along with the data
 Synchronous
 The transmitting and receiving devices are
synchronized
 A clock signal is transmitted along with the data (and is
used to synchronized the devices)
 Most (but not all) RS-232C interfaces are
asynchronous!
Asynchronous Data
Transmission
 Data are transmitted on the TD (transmit data)
line in packets, typically, of 7 or 8 bits
 Each packet is “framed” by a “start bit” (0) at the
beginning, and a “stop bit” (1) at the end
 Optionally, a “parity bit” is inserted at the end of
the packet (before the stop bit)
 The parity bit establishes either “even parity” or
“odd parity” with the data bits in the packet
 E.g., even parity: the total number of bits “equal to 1”
(including the data bits and the parity bit) is an “even
number
1’s and 0’s in RS-232C
 A “1” is called a “mark”
 A “0” is called a “space”
 The idle state for an RS-232C line is a 1
(“mark”)
 Idle state is called “marking the line”
 Voltages on an RS-232C line
 Well… that’s another story, and it’s not really a
concern to us
Data Transmission Example
 Plot of the asynchronous RS-232C
transmission of the ASCII character ‘a’ with
odd parity:
Idle
state
TD
0
1
0
Idle
state
Stop
bit
Start
bit
0
0
0
1
1
0
1
time
ASCII character ‘a’
• 7 bits
• LSB first
Parity
bit
RS-232C Connectors
 The original standard specified a 25-pin
connector
 Today, a 9-pin connector is more common
 E.g.,
DB9P
Note:
•P = “pin”
•Sometimes called a “male” connector
•The mate for this is a DP25S, or
“socket” connector – the “female”
RS-232C Connectors
Pin 1
Pin 1
Where is pin
1?
DB25P
DB25S
DB9P
DB9S
Pin 1
Pin 1
Where are pins 2, 3, 4,
etc.?
RS-232C Pins, Signals, Directions
Pin
DB25 DB9
1
2
2
3
3
4
7
5
8
6
6
7
5
8
1
20
4
22
9
Signal Name
CD
Chassis Ground
TD
Transmit Data
RD
Receive Data
RTS Request To Send
CTS Clear To Send
DSR Data Set Ready
SG
Signal Ground
DCD Data Carrier Detect
DTR Data Terminal Ready
RI
Ring Indicator
Direction
DTE  DCE
DTE  DCE
DTE  DCE
DTE  DCE
DTE  DCE
DTE  DCE
DTE  DCE
DTE  DCE
Universal Serial Bus (USB)
 A serial standard for connecting devices.
 Up to 127 devices can be connected to the
USB bus.
 USB current standard is USB 2.0 which
supports a transfer rate of 480Mbps.
USB Connectors and Hubs
USB A and B
female
connector
USB Hub
USB male A
connector
USB male B
connector
USB
 The USB bus is a [Differential] Bi-directional serial
interface cable bus. Differential NRZI data is transmitted
Isochronous or Asynchronous between devices. Data is
transferred at three different rates over a maximum
cable length of 4 meters ~ over 4 wires, 2 of which carry
data on a balanced twisted pair.
 USB 3.0 (Super-Speed USB) increases the data rate to 4.8
Gbit/s, 600 MB/s. USB 3.0 ports and cabling are designed
to enable backward compatibility, so the new connector
and cable contains both a USB 3.0 interface and a USB
2.0 interface.
NRZ
 "A type of 'null' encoding, where a logical 'zero' is
represented by a particular line state, and a logical 'one'
by another. In other words, there is no encoding, as
distinct from RZ encoding." NRZ is used with RS-232 and
CANbus.

A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
Parallel Interfaces
 History
 In the context of PCs, a “parallel interface” implies a
Centronics-compatible printer interface
 Originally developed by printer company, Centronics
 Introduced on the IBM PC (1981) as an LPT (“line
printer”) port
 Improvements
 EPP (Enhanced Parallel Port), development by Intel, Xircom,
Xenith
 Enshrined in the standard IEEE-1284 (1994)
 “Standard Signaling Method for a Bi-directional Parallel Peripheral
Interface for Personal Computers”
 Includes Centronics/LPT mode, EPP mode, and…
 ECP mode (Enhanced Capability Port)
Parallel Interfaces
 Data Rate
 150 Kbytes/s (LPT) to 1.5 Mbytes/s (ECP)
 Configuration
 Parallel, point-to-point
Typical Printer Cable
DB25P (male)
• Connects to PC
Centronics male
• 36 pins
• Connects to printer
Pinouts
Direction
out
out
out
out
out
out
out
out
out
in
in
in
in
out
in
out
out
-
DB25
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18-25
Cent.
Pin
1
2
3
4
5
6
7
8
9
10
11
12
13
14
32
31
36
19-30,
33,17,16
Signal
/Strobe
Data0
Data1
Data2
Data3
Data4
Data5
Data6
Data7
/Ack
Busy
PaperEnd
SelectIn
/AutoFd
/Error
/Init
/Select
Ground
Function
low pulse (>0.5 µs) to send
LSB
.
.
.
.
.
.
MSB
Low pulse ack. (~5 µs)
High for busy/offline/error
High for out of paper
High for printer selected
Low to autofeed one line
Low for Error
Low pulse (>50 s) to init
Low to select printer
-
A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
SCSI (1 of 2)
 Small Computer Systems Interface
 pronounced “scuzzy”
 History
 Developed by Shugart Associates (1981)
 Originally called Shugart Associates Systems Interface
(SASI, pronounced “sassi”)
 Scaled down version of IBM’s System 360 Selector
Channel
 Became an ANSI standard in 1986
 Used for…
 Disk drives, CD-ROM drives, tape drives, scanners,
printers, etc.
p. 232
SCSI (2 of 2)
 Configuration
 Parallel, daisy chain
 Requires terminator at end of chain
 Versions (data width, data rate)






SCSI-1, Narrow SCSI (8 bits, 5 MBps)
SCSI-2 (8, bits 10 MBps)
SCSI-3 (8, bits, 20 MBps)
UltraWide SCSI (16 bits, 40 MBps)
Ultra2 SCSI (8 bits 40 MBps)
Wide Ultra2 SCSI (16 bits, 80 MBps)
SCSI Block Diagram
System bus
or
I/O bus
SCSI bus
controller
SCSI port
I/O
device
I/O
device
SCSI bus
Terminator
I/O
device
SCSI Connectors
Narrow
SCSI
50 pins
50 pins
Fast
SCSI
Fast Wide
SCSI
68 pins
80 pins
Ultra
SCSI
Putting it all together
LPT
port
COM1 COM2
port
port
SCSI
port
Parallel
interface
Serial
interface
SCSI
interface
ISA or PCI
bus interface
CPU/system
bus
ISA or PCI
bus
A Detailed Look
 Let’s look at a few of the preceding examples in
more detail
 ISA
 PCI
 AGP
 Serial
 Parallel
 SCSI
 Ethernet
Ethernet Interfaces
 History
 In 1980, Xerox, Digital Equipment Corporation (DEC,
now Compaq), and Intel published a specification for
an “Ethernet” LAN (local area network)
 Now exists as a standard - IEEE 802.3
 Physical interface uses either coax cable with BNC connectors
or twisted pair cable with RJ-45 connectors (10Base-T)
 Fast Ethernet
 Specified in IEEE 802.3u (100Base-TX)
Ethernet Interfaces
 Data Rate
 10 Mbits/s for Ethernet (10Base-T)
 100 Mbits/s for Fast Ethernet (100Base-TX)
 Configuration
 Serial, multi-point (token ring or token bus)
Token Bus
Token Ring
Ethernet Adapter Example - PCI
Addtron
AEF-360TX
RJ-45
connector
BNC
connector
PCI
bus interface
RJ-45 Pinouts
1
8
Pin
1
2
3
4
5
6
7
8
Signal
TD+
TDRD+
RD-
Direction




-
Function
Transmit data
Transmit data return
Receive data
Receive data return
-
Ethernet Family
Protocol
--
Frequency
Distance
Cable
--
10Base-2
MHz
10
Meter
183
10Base-5
10
500
Coax
10Base-T
10
100
STP/UTP
10Base-F
10
1000
Fiber
100Base-T
100
100
STP/UTP
100Base-T4
100
100
STP/UTP
100Base-TX
100
100
STP/UTP
100Base-FX
100
--
Fiber
Coax
OSI: Open Systems Interconnect
OSI and Protocol Stack
OSI Model
TCP/IP Hierarchy
Protocols
7th
Application Layer
6th
Presentation Layer
Application Layer
5th
Session Layer
4th
Transport Layer
Transport Layer
3rd
Network Layer
Network Layer
2nd
Link Layer
1st
Physical Layer
Link Layer
Link Layer
: includes device driver and network interface card
Network Layer : handles the movement of packets, i.e. Routing
Transport Layer : provides a reliable flow of data between two hosts
Application Layer : handles the details of the particular application
63
Packet Encapsulation
 The data is sent down the protocol stack
 Each layer adds to the data by prepending headers
22Bytes 20Bytes 20Bytes
64 to 1500 Bytes
4Bytes
64
Ethernet
 Computer <-> Computer communication on
same network
 Each device has unique MAC address (48-bit)
example: 00-C0-4F-48-47-93
Ethernet Packet:
Preamble
8bytes
Dest.
address
6bytes
Source
address
6bytes
Type
2bytes
Data
64 - 1500bytes
CRC
4bytes
MAC: Media Access Control
65
ARP : Address Resolution Protocol

ARP provides mapping
32bit IP address <-> 48bit MAC address
128.97.89.153 <-> 00-C0-4F-48-47-93

ARP cache
maintains the recent mappings from IP addresses to MAC addresses
Protocol
1. ARP request broadcast on Ethernet
2. Destination host ARP layer responds
66
IP: Internet Protocol
 Unreliable … connectionless datagram delivery service
 Responsible for routing of data through intermediate
networks and computers
IP header:
1 :ICMP
6 :TCP
17 :UDP
0123
4567
11
8901
1111
2345
1111
6789
2222
0123
2222
4567
2233
8901
IP Routing
Source
Destination
Application
Application
Transport
Router
Transport
Network
Network
Network
Link
Link
Link
 Routing Table
Destination IP address
IP address of a next-hop router
Flags
Network interface specification
68

ICMP : Internet Control Message
Protocol
Used
to report problems with delivery of IP Datagrams within
an IP network
 Used by Ping, Tracerout commands
ICMP Message
20bytes
IP
Header
4bytes
ICMP
Header
Types and Codes
Type
Code
 Echo Request (type=8, code=0)
1byte
1byte
 Echo Reply(type=0, code=0)
 Destination Unreachable(type=3, code=0)
 Time Exceeded(type=11, code=0) : Time-to-Live =0
ICMP
Data
Checksum
2bytes
69
TCP : Transmission Control Protocol

Connection-Oriented, Reliable, Byte Stream Service
Protocol
1. Set up connection
2. Transfer data
3. Close connection
TCP Header Format
0
1
2
3
4
5
6
7
8
9
1
0
1
1
1
2
1
3
1
4
1
5
1
6
1
7
1
8
1
9
2
0
Source Port
2
1
2
2
2
3
2
4
2
5
2
6
2
7
2
8
2
9
3
0
3
1
Destination Port
Sequence Number
Acknowledgement Number
Data
Offset
-
-
-
-
Window
Checksum
Urgent Pointer
Options (0 to 10 Words of 32 Bits)
TCP Payload
70
TCP : Connection
Client
Host
Send SYN seq=x
Receive SYN
+ACK segment
Client
Host
Send FIN seq=x
Receive SYN segment
Send SYN seq=y,
ACK x+1
Receive ACK segment
Receive FIN
+ ACK segment
Send ACK y+1
Send ACK y+1
Receive ACK segment
Establishing a TCP Connection
Receive FIN segment
Send ACK x+1
Send FIN seq=y,
ACK x+1
Receive ACK segment
Closing a TCP Connection
71
TCP : Data transfer
Client
Timer
Send Packet 1
Start Timer
ACK would normally
Arrive at this time
Host
Packet Lost
Packet should arrive
ACK should be sent
Time Expires
Timer
Retransmit Packet1
Start Timer
Receive Packet 1
Send AXK 1
Receive ACK 1
Cancel Timer
72
Checksum
•Checksum - Probably one of the oldest methods of ensuring that data is correct,
checksums also provide a form of authentication because an invalid checksum
suggests that the data has been compromised in some fashion. A checksum is
determined in one of two ways
1.If the sum of the other bytes in the packet is 255 or less, then the checksum
contains that exact value.
2.If the sum of the other bytes is more than 255, then the checksum is the
remainder of the total value after it has been divided by 256.
• Let's look at a checksum example:
•1,151 / 256 = 4.496 (round to 4)
•4 x 256 = 1,024
•1,151 - 1,024 = 127
Byte 1
Byte 2
Byte 3
Byte 4
Byte 5
Byte 6
Byte 7
Byte 8
Total
Checksu
m
212
232
54
135
244
15
179
80
1,151
127
CRC
 Cyclic Redundancy Check (CRC) - CRCs are similar in
concept to checksums, but they use polynomial division
to determine the value of the CRC, which is usually 16 or
32 bits in length. The good thing about CRC is that it is
very accurate. If a single bit is incorrect, the CRC value
will not match up. Both checksum and CRC are good for
preventing random errors in transmission but provide
little protection from an intentional attack on your data.
Symmetric- and public-key encryption techniques are
much more secure.