I O Part 2

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I / O Part 2

• ECE-445
• Computer Organization
• Dr. Ron Hayne
• Electrical and Computer Engineering

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Buses

• Bus lines
• Data
• Address
• Control
• Timing
• Synchronous
• Asynchronous
• Device roles
• Master (initiator)
• Slave (target)

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Synchronous Bus
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Multiple-Cycle Transfers
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Asynchronous Bus (Input)
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Asynchronous Bus (Output)
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Interface Circuits

• Port
• Datapath and associated controls to transfer data
  between interface and the I/O device
• Parallel
• Number of bits simultaneously
• Serial
• One bit at a time

• I/O Interface
• Storage buffer
• Status flags
• Address decoder
• Timing signals
• Format conversion
• parallel-serial

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Parallel Port (Input)
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Parallel Port (Output)
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General Parallel Interface
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Serial Port

• Bit-serial on device side
• Bit-parallel on bus side
• Shift registers
• serial-in, parallel-out
• parallel-in, serial out
• Double buffering
• Example
• Universal Asynchronous Receiver Transmitter (UART)

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Example Serial Interface
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Universal Serial Bus (USB)

• Design objectives
• Simple, low-cost, easy to use
• Wide range of I/O devices
• "Plug-and-play"
• Connect while system is operating
• Auto detection/configuration
• Operating speeds
• Low-speed 1.5 megabits/s
• Full-speed 12 megabits/s
• High-speed 480 megabits/s (USB 2.0)

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USB Architecture
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USB Operation

• Polling
• Device may send a message only in response to a
  poll from the host (one at a time)
• Pipes
• Bidirectional communications links between
  application software (device drivers) and I/O
  devices
• Addressing
• Each device assigned 7-bit address
• Endpoints
• Location in a device to or from which data can be
  transfered
• 4-bit ID (input/output pair)

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USB Protocols

• Packets
• One or more bytes of info
• Control
• Data
• Packet Fields
• Packet identifier (PID)
• Address (ADDR)
• Endpoint (ENDP)
• Cyclic reduncancy check (CRC)
• 5 bit error checking for tokens
• 16 bit error checking for data

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USB Packet Formats
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USB Output Transfer
Host
Hub
I/ODevice
Time
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Input Devices

• Keyboard
• Characters
• Mouse
• X-Y
• Mechanical
• Optical
• Trackball, Joystick, Touchpad
• X-Y
• Scanner
• Bit-mapped image

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Output Devices

• Video Displays
• Pixels
• CRT
• LCD
• Printers
• Pixles, characters
• Laser
• Ink jet
• Graphics Accelerators
• Graphics processing

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Modem

• MOdulator-DEModulator
• Asynchronous transmission
• 56K (bits/sec)

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DSL

• Digital Subscriber Loop
• Twisted-pair wiring
• Asymetric DSL
• Different transmission speeds upstream and
  downstream
• Time Division Multiplexing (channels)
• Telephone
• Upstread data
• Downstream data

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DSL Connection
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Cable Modem

• Coaxial Cable
• Higher bandwidth
• Bus-like connection
• Share capacity

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Cable Modem Connection
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Questions?