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5.2 NEED FOR AN INTERFACE

  • Input-Output Interface:

    • Facilitates the transfer of information between internal storage devices (e.g., memory) and external peripheral devices.

    • Peripheral devices can be categorized as:

      • Input Devices: Examples include keyboard and mouse, which supply data to the computer.

      • Output Devices: Examples include monitors and printers, which output data from the computer.

      • I/O Devices: Some devices can provide both input and output (e.g., external hard drives).

  • Micro-computer Base System:

    • Peripheral devices serve to create communication links with the CPU.

    • Differences between peripheral devices and CPU necessitate special communication links.

    1. Nature:

      • Peripheral Devices: Electromagnetic and electro-mechanical.

      • CPU: Electronic.

    2. Speed: Peripheral devices have slower synchronization mechanisms compared to the CPU.

    3. Data Formats: Peripheral devices and memory use different data formats.

    4. Operating Modes: Peripheral devices have distinct operation modes to ensure they do not disturb other devices.

5.5 FUNCTIONS OF INPUT-OUTPUT INTERFACE

  • Synchronization: Ensures the operating speed of the CPU matches with input-output devices.

  • Device Selection: Chooses appropriate input-output devices for data interpretation.

  • Signal Provisioning: Provides control and timing signals.

  • Data Buffering: Facilitates buffering through the data bus.

  • Error Detection: Includes multiple error detectors.

  • Data Conversion:

    • Converts serial data to parallel and vice-versa.

    • Converts digital data to analog and vice-versa.

5.3 THREE MODES OF DATA TRANSFER

  1. Data Transfer Types: Transfers can occur between:

    • CPU and Memory

    • CPU and I/O Devices

    • Memory and I/O Devices

  2. Transfer Methodologies:

    • Programmed Data Transfer: CPU monitors and controls the transfer process.

    • Direct Memory Access (DMA): Allows peripherals to communicate directly with memory bypassing CPU involvement.

5.6 COMPUTER ARCHITECTURE

Data Transfer Modes

  • Synchronous Transfer: Uses common clock pulses for data transfer (e.g., chat rooms, video conferencing).

  • Asynchronous Transfer: Does not require synchronized timing; operates with start and stop bits (e.g., telephonic conversations).

Strobe Controlled Procedure

  • Mechanism: Uses a single control line to time transfers, allowing source or destination units to initiate data transfer.

5.7 HANDSHAKING PROCEDURE OF DATA TRANSFER

  • Definition: Handshaking synchronizes data transfer by sending signals between source and destination units to confirm data readiness.

  • Signal Exchange: For every direction of data flow, a corresponding control signal ensures data integrity during transfer.

5.9 DMA CONTROLLED TRANSFER

  • Direct Memory Access (DMA):

    • Allows peripherals to communicate directly with memory units without CPU intervention, improving efficiency.

    • Types of DMA Transfer:

      1. Burst Transfer: Transfers an entire block of data before relinquishing the bus control.

      2. Cycle Stealing: Transfers one word at a time, allowing CPU to resume its operations in intervals.

      3. Interleaved Mode: Using the bus during CPU idle periods for efficient data transfers.

5.10 PRIORITY INTERRUPT, POLLING, AND DAISY CHAINING

  • Priority Interrupts: Determine which device with simultaneous requests gets serviced first, giving priority to faster devices like magnetic disks.

  • Types of Interrupts:

    1. Hardware Interrupts: Triggered by external devices.

    2. Software Interrupts: Caused by internal software actions.

  • Daisy Chaining: A series connection of devices; higher priority devices are serviced first.

5.11 INPUT OUTPUT PROCESSOR

  • Input-Output Processor (IOP):

    • Manages input-output tasks independently of the CPU, allowing direct data transfer between peripherals and memory.

    • The CPU assigns I/O tasks, while the IOP handles execution.

5.12 BUS SYSTEMS

Types of System Buses

  1. Control Bus: Information on data transfer methods.

  2. Data Bus: Carries actual data.

  3. Address Bus: Indicates addresses of accessed data.

Functionality of Buses

  • Data buses facilitate communication between various computer components, ensuring coordinated transfers.