MODULE: 1
After this module we you will be able to understand:-
1)What is a microprocessor
2)Classification of microprocessor
3)8085 architecture
4)8085 pin diagram
5)Classification of instruction set of 8085
5.1)Based on Functionality
5.2)Based on length
5.3)Based on Addressing modes
6)Timing diagrams
6.1)Opcode fetch
6.2)Memory Read
6.3)Memory Write
6.4)I/O Read
6.5)I/O Write
, 1)INTRODUCTION TO MICROPROCESSOR:
A microprocessor is a programmable electronics chip that has computing and decision-
making capabilities similar to central processing unit of a computer. Any microprocessor-
based systems having limited number of resources are called microcomputers. Nowadays,
microprocessor can be seen in almost all types of electronics devices like mobile phones,
printers, washing machines etc.
Microprocessors are also used in advanced applications like radars, satellites and flights.
Due to the rapid advancements in electronic industry and large scale integration of devices
results in a significant cost reduction and increase application of microprocessors and their
derivatives.
Fig.1
Microprocessor-based system
Basic details you need to know:-
• Bit: A bit is a single binary digit.
• Word: A word refers to the basic data size or bit size that can be processed by the
arithmetic and logic unit of the processor.
A 16-bit binary number is called a word in a 16-bit processor.
• Bus: A bus is a group of wires/lines that carry similar information.
,• System Bus: The system bus is a group of wires/lines used for communication between the
microprocessor and peripherals.
• Memory Word: The number of bits that can be stored in a register or memory element is
called a memory word.
• Address Bus: It carries the address, which is a unique binary pattern used to identify a
memory location or an I/O port.
For example, an eight bit address bus has eight lines and thus it can address 28 = 256
different locations.
The locations in hexadecimal format can be written as 00H – FFH.
• Data Bus: The data bus is used to transfer data between memory and processor or between
I/O device and processor.
For example, an 8-bit processor will generally have an 8-bit data bus and a 16-bit processor
will have 16-bit data bus.
• Control Bus: The control bus carry control signals, which consists of signals for selection
of memory or I/O device from the given address, direction of data transfer and
synchronization of data transfer in case of slow devices.
A typical microprocessor consists of arithmetic and logic unit (ALU) in association with
control unit to process the instruction execution. Almost all the microprocessors are based
on the principle of store-program concept. In store-program concept, programs or
instructions are sequentially stored in the memory locations that are to be executed.
To do any task using a microprocessor, it is to be programmed by the user. So, the
programmer must have idea about its internal resources, features and supported instructions.
Each microprocessor has a set of instructions, a list which is provided by the microprocessor
manufacturer.
The instruction set of a microprocessor is provided in two forms: binary machine code and
mnemonics. Microprocessor communicates and operates in binary numbers 0 and 1.The set
of instructions in the form of binary patterns is called a machine language and it is difficult
for us to understand.
Therefore, the binary patterns are given abbreviated names, called mnemonics, which forms
the assembly language. The conversion of assembly-level language into binary machine-
level language is done by using an application called assembler.
, 2)Classification of Microprocessors:
Based on their specification, application and architecture microprocessors are classified.
Based on size of data bus:
• 4-bit microprocessor
• 8-bit microprocessor
• 16-bit microprocessor
• 32-bit microprocessor
Based on application:
• General-purpose microprocessor- used in general computer system and
can be used by programmer for any application. Examples, 8085 to Intel
Pentium.
• Microcontroller- microprocessor with built-in memory and ports and can
be programmed for any generic control application. Example, 8051.
• Special-purpose processors- designed to handle special functions required
for an application. Examples, digital signal processors and application-
specific integrated circuit (ASIC) chips.
Based on architecture:
• Reduced Instruction Set Computer (RISC) processors
• Complex Instruction Set Computer (CISC) processors
3)8085 MICROPROCESSOR ARCHITECTURE
The 8085 microprocessor is an 8-bit processor available as a 40-pin IC package and uses
+5 V for power.
-It can run at a maximum frequency of 3 MHz.
-Its data bus width is 8-bit and address bus width is 16-bit, thus it can address 216 = 64
KB of memory.
-The internal architecture of 8085 is shown is above figure.
After this module we you will be able to understand:-
1)What is a microprocessor
2)Classification of microprocessor
3)8085 architecture
4)8085 pin diagram
5)Classification of instruction set of 8085
5.1)Based on Functionality
5.2)Based on length
5.3)Based on Addressing modes
6)Timing diagrams
6.1)Opcode fetch
6.2)Memory Read
6.3)Memory Write
6.4)I/O Read
6.5)I/O Write
, 1)INTRODUCTION TO MICROPROCESSOR:
A microprocessor is a programmable electronics chip that has computing and decision-
making capabilities similar to central processing unit of a computer. Any microprocessor-
based systems having limited number of resources are called microcomputers. Nowadays,
microprocessor can be seen in almost all types of electronics devices like mobile phones,
printers, washing machines etc.
Microprocessors are also used in advanced applications like radars, satellites and flights.
Due to the rapid advancements in electronic industry and large scale integration of devices
results in a significant cost reduction and increase application of microprocessors and their
derivatives.
Fig.1
Microprocessor-based system
Basic details you need to know:-
• Bit: A bit is a single binary digit.
• Word: A word refers to the basic data size or bit size that can be processed by the
arithmetic and logic unit of the processor.
A 16-bit binary number is called a word in a 16-bit processor.
• Bus: A bus is a group of wires/lines that carry similar information.
,• System Bus: The system bus is a group of wires/lines used for communication between the
microprocessor and peripherals.
• Memory Word: The number of bits that can be stored in a register or memory element is
called a memory word.
• Address Bus: It carries the address, which is a unique binary pattern used to identify a
memory location or an I/O port.
For example, an eight bit address bus has eight lines and thus it can address 28 = 256
different locations.
The locations in hexadecimal format can be written as 00H – FFH.
• Data Bus: The data bus is used to transfer data between memory and processor or between
I/O device and processor.
For example, an 8-bit processor will generally have an 8-bit data bus and a 16-bit processor
will have 16-bit data bus.
• Control Bus: The control bus carry control signals, which consists of signals for selection
of memory or I/O device from the given address, direction of data transfer and
synchronization of data transfer in case of slow devices.
A typical microprocessor consists of arithmetic and logic unit (ALU) in association with
control unit to process the instruction execution. Almost all the microprocessors are based
on the principle of store-program concept. In store-program concept, programs or
instructions are sequentially stored in the memory locations that are to be executed.
To do any task using a microprocessor, it is to be programmed by the user. So, the
programmer must have idea about its internal resources, features and supported instructions.
Each microprocessor has a set of instructions, a list which is provided by the microprocessor
manufacturer.
The instruction set of a microprocessor is provided in two forms: binary machine code and
mnemonics. Microprocessor communicates and operates in binary numbers 0 and 1.The set
of instructions in the form of binary patterns is called a machine language and it is difficult
for us to understand.
Therefore, the binary patterns are given abbreviated names, called mnemonics, which forms
the assembly language. The conversion of assembly-level language into binary machine-
level language is done by using an application called assembler.
, 2)Classification of Microprocessors:
Based on their specification, application and architecture microprocessors are classified.
Based on size of data bus:
• 4-bit microprocessor
• 8-bit microprocessor
• 16-bit microprocessor
• 32-bit microprocessor
Based on application:
• General-purpose microprocessor- used in general computer system and
can be used by programmer for any application. Examples, 8085 to Intel
Pentium.
• Microcontroller- microprocessor with built-in memory and ports and can
be programmed for any generic control application. Example, 8051.
• Special-purpose processors- designed to handle special functions required
for an application. Examples, digital signal processors and application-
specific integrated circuit (ASIC) chips.
Based on architecture:
• Reduced Instruction Set Computer (RISC) processors
• Complex Instruction Set Computer (CISC) processors
3)8085 MICROPROCESSOR ARCHITECTURE
The 8085 microprocessor is an 8-bit processor available as a 40-pin IC package and uses
+5 V for power.
-It can run at a maximum frequency of 3 MHz.
-Its data bus width is 8-bit and address bus width is 16-bit, thus it can address 216 = 64
KB of memory.
-The internal architecture of 8085 is shown is above figure.
