Lecture 2
Microcomputer Organization:
As discussed in previous lecture microprocessor is a central
processing unit (CPU) with its related timing functions on a single
chip. A microprocessor combined with memory and input/output
devices forms a microcomputer. Therefore, the basic components of
a microcomputer are:
1) CPU
2) Program memory
3) Data memory
4) Output ports
5) Input ports
6) Clock generator.
These components are shown in fig.1.1 below:
Program Data
memory memory
Clock Output
generator CPU ports
Input
ports
Fig.1.1 Basic Components of Microcomputer
, Central Processing Unit:
The CPU consists of ALU (Arithmetic and Logic Unit), register
unit and control unit. The CPU fetches the stored instructions from
the program memory, data word from data memory or from an input
device and after processing the data stores the result in data memory
or sends it to an output device.
a) ALU (Arithmetic and Logic Unit)
This unit performs computing functions on m-bit data where ‘m’
is the bit size of the processor. These functions are arithmetic
operations such as addition, subtraction and logical operation such as
AND, OR, XOR, rotate, compare etc. Results are stored either in
registers or in memory or sent to output devices.
b) Register Unit:
It contains various 8-bit or 16-bit registers. These registers are
used primarily to store data temporarily during the execution of a
program. Some of the registers are accessible to the user through
instructions. It means there contents can be read and/or changed
through instructions. Some of the registers are not accessible to user
but they are used by the processor for the execution of an instruction.
8085A microprocessor contains 8-bit registers such as Accumulator
(Reg. A), B, C, D, E, H, L etc and16-bit registers such as Program
Counter (PC), Stack Pointer (SP).
Microcomputer Organization:
As discussed in previous lecture microprocessor is a central
processing unit (CPU) with its related timing functions on a single
chip. A microprocessor combined with memory and input/output
devices forms a microcomputer. Therefore, the basic components of
a microcomputer are:
1) CPU
2) Program memory
3) Data memory
4) Output ports
5) Input ports
6) Clock generator.
These components are shown in fig.1.1 below:
Program Data
memory memory
Clock Output
generator CPU ports
Input
ports
Fig.1.1 Basic Components of Microcomputer
, Central Processing Unit:
The CPU consists of ALU (Arithmetic and Logic Unit), register
unit and control unit. The CPU fetches the stored instructions from
the program memory, data word from data memory or from an input
device and after processing the data stores the result in data memory
or sends it to an output device.
a) ALU (Arithmetic and Logic Unit)
This unit performs computing functions on m-bit data where ‘m’
is the bit size of the processor. These functions are arithmetic
operations such as addition, subtraction and logical operation such as
AND, OR, XOR, rotate, compare etc. Results are stored either in
registers or in memory or sent to output devices.
b) Register Unit:
It contains various 8-bit or 16-bit registers. These registers are
used primarily to store data temporarily during the execution of a
program. Some of the registers are accessible to the user through
instructions. It means there contents can be read and/or changed
through instructions. Some of the registers are not accessible to user
but they are used by the processor for the execution of an instruction.
8085A microprocessor contains 8-bit registers such as Accumulator
(Reg. A), B, C, D, E, H, L etc and16-bit registers such as Program
Counter (PC), Stack Pointer (SP).
