Presiding Officer Training module 2024 lok sabha elections
IT in Business Lecture on Machine Cycles and Computer Buses
1. L E C T U R E 3
O C T O B E R , 2 0 1 8
IT in Business - I
2. Machine cycles
• Each time the CPU executes an instruction, it takes a series of steps.
• The completed series of steps is called machine cycles.
• A machine cycle itself can be broken down into two smaller cycles-
1. Instruction cycle
2. Execution cycle
3. Instruction Cycle
At the beginning of machine cycle (that is during
the instruction cycle), The CPU takes two steps:
INSTRUCTION CYCLE
1. FETCHING:
• Before CPU can execute an instruction ,the control unit must retrieve a
command or data from the computer’s main memory.
2. DECODING:
• Before a command can be executed ,the control unit must break down (or
decode) the command into instruction that correspond to those in the CPU’s
instruction set
4. Execution Cycle
At this point, the CPU is ready to begin
the execution cycle:
Execution Cycle
1.Executing:
When the command is executed, the CPU carries out the instructions in order.
2. Storing:
The CPU may be required to store the results of an instruction in memory (but
this condition is not always required).
7. Computer Bus
Computer Bus can be define as
“A bus, in computing, is a set of physical connections
(cables, printed circuits, etc.) which can be shared by
multiple hardware components in order to communicate
with one another. ”
Purpose:
The purpose of buses is to reduce the number of
"pathways" needed for communication between the
components, by carrying out all communications over a
single data channel. This is why the metaphor of a "data
highway" is sometimes used.
8. Computer Bus
A bus is characterized by the amount of information that
can be transmitted at once.
This amount, expressed in bits, corresponds to the
number of physical lines over which data is sent
simultaneously.
A 32-wire ribbon cable can transmit 32 bits in parallel.
The term "width" is used to refer to the number of bits
that a bus can transmit at once.
Additionally, the bus speed
is also defined by
its frequency (expressed in
Hertz), the number of data
packets sent or received per
second. Each time that data
is sent or received is called
a cycle
9. Architecture /Types
Computer Bus
There are following types of Buses available in Computer System.
Data Bus
Address Bus
Control Bus
10. Data Bus
The electronic path through which data is transferred between components of computer is called data
bus.
The data bus typically consists of 8,16,32,64 separate lines
The data bus transfers instructions coming from or going to the processor. It is a bidirectional bus. It
means that the CPU can
Read data from memory using these lines.
Write data to memory locations using these line
Different devices such as key board, memory and mouse
work with data bus.
11. Address Bus
The address bus (sometimes called the memory bus) transports memory addresses which
the processor wants to access in order to read or write data.
It is a unidirectional bus.
The address bus is used to designate the source or destination of data on the data bus.
The address bus typically consists of 8,16 or 32 separate lines.
The address is sent out in binary form.
Each address lines carries ‘1’ or ‘0’value
The number of address line determines the number of memory locations that CPU can address.
12. Control Bus
The Control bus (or command bus) transports orders and synchronization
signals coming from the control unit and travelling to all other hardware
components.
It is a bidirectional bus, as it also transmits response signals from the hardware.
The control buses are used to control the use of the data and address buses.
CPU provide enabling signal through control bus.
For example:
Many devices are connected to data bus like keyboard, mouse etc, but only one
should be enabled at a given time. It is controlled by control bus.
15. What are Ports?
On computer, a port is generally a
specific place for being physically
connected to some other device,
usually with a socket or plug
which we call Connectors.
There are following types of ports
available in computer system
◦ Parallel Port
◦ Serial Port
◦ USB port
◦ RGB Display Port
◦ A/V Port
16. Parallel Port
The printer connects to your
computer with a Parallel connector.
This connector has 25 pins.
Parallel means the device is capable
of receiving more than one bit at a
time (that is, it receives several bits in
parallel).
17. Serial Ports
Serial ports are universal I/O ports. They are
available on almost every computer.
Serial ports are slow used for terminal
connections, modem connections, keyboards,
mice, and other input/output devices.
18. Serial Port
Also used for Network connections and for connecting devices such as
Digital Cameras
