I/O INTERFACE (Input/Output Interface)

I/O Interface acts as an intermediate hardware unit between the CPU and peripheral devices to ensure smooth data transfer by matching speed, data format, and control signals.

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Need for I/O Interface

1. Speed mismatch –
2. Data format mismatch –
3. Control and timing mismatch –
4. Device selection and identification -
5. Data buffering-

 

Block Diagram of I/O Interface

       

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Main Components of I/O Interface

1 Address Decoder

• Identifies the I/O device by address.

2 Data Register

• Holds data being transferred between the CPU and the I/O device

3 Control Register

• Stores control commands from CPU (READ, WRITE, START, STOP)

4 Status Register

• Contains device status information. Examples: Ready, Busy, Error

5 Buffer

• Temporarily stores data
• Handles speed mismatch between CPU and device

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Types of I/O Interfaces

1 Serial Interface

• Transfers 1 bit at a time
• Slow but cost-effective
• Examples: USB, RS-232

2 Parallel Interface

• Transfers multiple bits simultaneously
• Faster than serial
• Examples: Printer, Parallel Port

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I/O Data Transfer Methods

7.1 Programmed I/O

• CPU continuously checks the device status
• CPU is busy waiting

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2 Interrupt-driven I/O

• The device interrupts the CPU when ready
• CPU performs other tasks meanwhile

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3 Direct Memory Access (DMA)

• DMA controller transfers data directly between memory and device
• CPU involvement minimal

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