INTRODUCTION TO COMPUTER SYSTEM ARCHITECTURE

40 III

EXAMPLE OF INTERFACE

Example of Interface :
Parallel – sometimes called LPT (“line printer”)
Serial – typically RS232C (sometimes RS422)
PS/2 – for keyboards and mice
USB – Universal Serial Bus
IrDA – Infrared Device Attachment
FireWire – new, very high speed, developed by IEEE InfiniBand

IVINPUT/OUTPUT
DATA TRANSFER

41 Asynchronous Serial Transfer
42 Asynchronous Communication

Interface

43 Mode Of Transfer

41 IV

ASYNCHRONOUS SERIAL
TRANSFER

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. Serial transmission can be
synchronous or asynchronous:-

In synchronous transmission, the two units share a common
clock frequency and bits are transmitted continuously at the
rate dictated by the clock pulse.

In asynchronous transmission, binary information is sent only
when it is available and the line remains idle when there is no
information is being transmitted.

42 IV

ASYNCHRONOUS
COMMUNICATION INTERFACE

A serial asynchronous data transmission technique used in
many interactive terminals employs special bits that are inserted
in both ends of the character code. With this technique, each
character consist of three parts which is Start bit, Character bit
and Stop bit.

Figure 4.1: Asynchronous Communication
Interface(https://www.slideshare.net/JackJivolin/computer-system-

architecture-173341721)

43 IV

MODE OF TRANSFER

MODE OF TRANSFER : PROGRAMMED I/O
With programmed I/O, data are exchanged between the
processor and the I/O module. The processor executes a
program that gives it direct control of the I/O operation,
including sensing device status, sending a read or write
command and transferring the data. When the processor issues
a command to the I/O module, it must wait until the I/O
operation is complete. If the processor is faster than the I/O
module, this is wasteful of processor time.

44 IV

MODE OF TRANSFER : INTERRUPT-INITIATED I/O

With interrupt-driven I/O, the processor issues an I/O command
that continues to execute other instructions 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 the main memory for output and
storing data in the 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.

45 IV

MODE OF TRANSFER : DIRECT MEMORY ACCESS

A direct memory access (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 as direct memory access (DMA). In this
mode, the I/O module and main memory exchange data
directly without processor involvement.

DMA controller services are usually provided by DMA controller,
which is itself a specialized processor that is transferring data
directly to or from I/O devices and memory. Many hardware
systems use DMA, including disk drive controllers, graphics
cards, network cards, and sound cards.

REFERENCES

1. Ledin. J. (2020). Modern Computer Architecture and

Organization: Learn x86, ARM,and RISC-V architectures

and the design of smartphones, PCs, and cloud servers 1st

Edition, Kindle Edition. Packt Publishing. India.

(ISBN:1838984399)

2. Stefano. M. (2020). Architecture Computer. Kindle
Edition. Amazon. (ASIN:B08NYX5VF3)

3. David. A. P. &. John. L. H. (2018). Computer Organization
and Design The Hardware / Software Interface (RISC-V
Edition). Book Aid International.(ISBN: 0128122757)

4. Stallings. W. (2018). Computer Organisation and
Architecture Design for Performance (11th Edition). United
State: Pearson Education. (ISBN:9780134997193)

5. John. L. H. & David. A. P. (2017). Computer Architecture A
Quantitative Approach Sixth Edition. Katey Birtcher. (ISBN:
0128119055)

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