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input output (I/O) data transfer in computer system, IMG-20240220-WA0000,โฆ
input output (I/O) data transfer in computer system
๐ ๐ข๐๐ ๐ข๐ ๐ง๐ฅ๐๐ก๐ฆ๐๐๐ฅ
๐ฃ๐ฟ๐ผ๐ด๐ฟ๐ฎ๐บ๐บ๐ฒ๐ฑ
๐/๐ข
data are exchanged between the processor and the I/O module
execute the program tha gives it direct control of the I/O outpu, sending a read or write command and transferring the data.
๐๐ถ๐ฟ๐ฒ๐ฐ๐ ๐ ๐ฒ๐บ๐ผ๐ฟ๐ ๐๐ฐ๐ฐ๐ฒ๐๐
DMA device can transfer data directly to and from memory rather than using the CPU as an intermediary, and can thus relieve congestion on the system bus.
The alternative is known direct memory access (DMA). In this mode, the I/O module and main memory exchange data directly, without processor involvement.
DMA Controller
๏จ Many hardware systems use DMA, including disk drive controllers, graphics cards, network cards
and sound cards.
๏จ DMA services are usually provided by DMA controller, which is, itself a specialized processor
whose specialty is transferring data directly to or from I/O devices and memory.
๐๐ป๐๐ฒ๐ฟ๐ฟ๐๐ฝ๐ ๐๐ฟ๐ถ๐๐ฒ๐ป ๐/๐ข
the processor issues an I/O
command, continues to execute other instruction, and is interrupted by the I/O module when the latter has completed its work.
With both programmed and interrupt I/O, the processor is responsible for extracting data from main memory for output and storing data in main memory for input.
With interrupt-driven I/O, the CPU does not access a
device until it needs servicing, and so it does not get
caught up in busy-waits.
In interrupt-driven I/O, the device requests service through a special interrupt request line that goes directly to the CPU.
Three Techniques for Input of a Block of Data
๐๐ฆ๐ฌ๐ก๐๐๐ฅ๐ข๐ก๐ข๐จ๐ฆ ๐ฆ๐๐ฅ๐๐๐ ๐ง๐ฅ๐๐ก๐ฆ๐๐๐ฅ
๐ฆ๐๐ป๐ฐ๐ต๐ฟ๐ผ๐ป๐ผ๐๐
๐๐ฟ๐ฎ๐ป๐๐บ๐ถ๐๐๐ถ๐ผ๐ป
the two units share a common clock frequency and bits are transmitted continuously at the rate dictated by the clock pulse
๐๐๐๐ป๐ฐ๐ต๐ฟ๐ผ๐ป๐ผ๐๐ ๐๐ฟ๐ฎ๐ป๐๐บ๐ถ๐๐๐ถ๐ผ๐ป
binary information is sent only when it is available and the line remains idle when there is no information is being transmitted.
๐ง๐ต๐ฒ ๐๐๐๐ป๐ฐ๐ต๐ฟ๐ผ๐ป๐ผ๐๐ ๐๐ผ๐บ๐บ๐๐ป๐ถ๐ฐ๐ฎ๐๐ถ๐ผ๐ป ๐๐ป๐๐ฒ๐ฟ๐ณ๐ฎ๐ฐ๐ฒ
A serial asynchronous data transmission technique used in many interactive terminals employs special
bits that are inserted in both ends of the character code.
Start bit
Character bit
Stop bit
Serial Transmission of Asynchronous
is done by two ways:
a) Asynchronous Communication Interface
b) First in First out Buffer (FIFO)
The transfer of data between two units may be done in parallel or serial. Serial transmission is slower but is less expensive since it requires one pair of conductors.
