COMPUTER ORGANISATION

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COMPUTER ORGANISATION

• Sri.C.R. Rajagopal
• Assistant Professor,
• Vivekananda Institute of Technology,
• Bangalore, INDIA

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Input/output Organization
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Objectives

• In this session, you will learn
• USB Features
• Limitations of USB
• Terminology used in USB
• USB Communications
• USB Controller
• Expected Questions

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Terminology used in USB

• Host
• Function
• Hub
• Devices
• Port

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Function of Host

• Detecting devices
• Management of data
• Error checking
• Provide power
• Exchange data with peripherals

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Peripheral Function

• Detecting communication directed to the chip
• Response to standard request
• Error checking
• Managing power
• Exchange data with the host

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USB Communication

• Configuration communication
• Application communication

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Elements of Transfer

• Device endpoint
• Pipes
• Connects endpoint to the host
• Transaction
• The building blocks of a transfer
• Phases of a transaction

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Data Transfer Types

• Control Transfer
• Bulk Transfer
• Interrupt Transfer
• Isochronous Transfer

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USB Controller

• Elements of a USB controller
• CPU
• Program Memory
• Data Memory
• Registers
• USB Port
• USB Buffers

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USB Architecture

• Each node of the tree has a device called a hub.
• A root hub connects the entire tree to the host
  computer.
• The leaves of the tree are the I/O Devices being
  served.
• The tree structure enables many devices to be
  connected while using only simple point-to-point
  serial links.

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USB Architecture
Host Computer
Root Hub
Hub
Hub
I/O Device
I/O Device
I/O Device
I/O Device
Hub
I/O Device
I/O Device
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Split Bus
Host Computer
Root Hub
HS
HS
Hub A
Hub B
HS
F/LS
HS - High speed F/LS - Full /Low speed
Device C
Device D
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Addressing

• Periodically the host polls the Hub
• After detecting the new device it sends the
  commands to send reset signal.
• Read the information from the device to know the
  capabilities.
• Send the configuration information to the device.
• Assign the device with unique USB address

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USB Protocols
PID3
PID1
PID2
PID0
PID3
PID2
PID1
PID0
Packet Identifier
Field
PID
ADDR
ENDP
CRC16
Token Packet IN or OUT
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16
0 to 8192
PID
DATA
CRC16
USB Packet Format
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Summary

• In this chapter we have discussed
• Different I/O transfers
• Interrupts
• DMA transfers
• Three popular interconnection standards
  PCI,SCSI,and USB

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Expected Questions

• Why I/O Devices can not be connected directly to
  the system bus?
• Give comparison between memory mapped I/O and I/O
  mapped I/O.
• What is an interrupt and ISR?
• What do you mean by single level interrupts and
  multi level interrupts?
• What do you mean by interrupts nesting?

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Expected Questions (contd.,)

• What do you mean by privilege exceptions?
• What do you mean by DMA channel?
• Explain centralized and distributed bus
  arbitration.
• List the features of PCI,SCSI and USB
• Explain the data transfer types in USB

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Thank you