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Understand I/O in computer system - Coggle Diagram
Understand I/O in computer system
I/O Data Transfer
Asynchronous Serial Transfer
Asynchronous serial transmission is character oriented.
Each character transmitter consists of a start bit,character bits,and stop bits.
Asynchronous Communication Interface
Is the transmission of data without the use of an external clock signal,where data can be transmitted continuously rather than in a steady stream
The most significant aspect of asynchronous communications is variable bit rate,or that the transmitter and receiver clock generators do not have to be exactly synchronized.
I/O Module Function
Acts as an interface with one or more peripheral devices by tailored data links.
Acts as an interface with the CPU and memory via the system bus or central switch.
Characteristic of isolated and memory mapped I/O
The processor and the I/O device have different memory located to each other.
Memory mapped I/O is one where the processor and the I/O device share the same memory location(memory).
Transfer mode
Interrupt-Initiated I/O
Direct memory Access
Programmed I/O
Interrupt-Initiated I/O
The processor does not have to repeatedly check the I/O module status.
Summary
No repeated CPU checking of device
I/O module interrupts when ready
Overcome CPU waiting
Overcomes the processor having to wait long periods of time for I/O modules.
Programmed I/O
Is the method of transfering data between the CPU and a peripheral such as a network adapter or an ATA storage device.
The best known example of a PC device that uses programmed I/O is the ATA interface.
Advantage
Simple to implement
Disadvantage
CPU is tied up for the duration of the transfer while doing a relatively simple task.
Direct Memory Access
Direct Memory Access is a method of transferring data between peripherals and memory without using the CPU.
Sometimes,CPU may not be fast enough to keep up with the peripheral.
Direct Memory Access Controller(DMAC)
The DMA controller periodically takes over control of the system bus from the CPU.
DMAC generates address,data and control signals to transfer data between memory and I/O devices.