2. Introduction to 8085
Microprocessor
• Microprocessor is a electronic chip, that functions as
the central processing unit of a computer.
• For example: Washing machines, microwave ovens,
mobile phones etc.
• Its advance applications are Radar, Satellites, flights.
• All processors are use the basic concept of stored
program execution. program or instructions are stored
sequentially in the memory. Every microprocessor has
its own associated set of instructions. Instruction
set for microprocessor is in two forms one in
mnemonic, which is comparatively easy to understand
and the other is binary machine code.
4. Introduction to Intel 8085
Microprocessor
• The Intel 8085 ("eighty-eighty-five") is an 8-bit
microprocessor introduced by Intel in 1977.
• The 8085 is a conventional von Neumann design
based on the Intel 8080. It is designed by using nmos
technology. The "5" in the model number came from
the fact that the 8085 requires only a +5-Volt (V)
power supply. rather than requiring the +5 V, −5 V and
+12 V supplies the 8080 needed. It has 8 bit data bus
and 16 bit address bus. it can work up to 5 MHz
frequency. It has 40 pins in its chip. Lower order
address bus is multiplexed with data bus to minimize
the chip size.
5. Introduction to Intel Microprocessor
• The 8085 has extensions to support new interrupts,
with three maskable interrupts (RST 7.5, RST 6.5 and
RST 5.5), one non-maskable interrupt (TRAP), and
one externally serviced interrupt (INTR). The RST n.5
interrupts refer to actual pins on the processor, a
feature which permitted simple systems to avoid the
cost of a separate interrupt controller.
6. Basic features of 8085
• 8085 is single chip 8-bit microprocessor.
• 8085 microprocessor provides on chip clock
generator.
• One accumulator, one flag register, 6 General
Purpose registers and 2 special purpose register.
• 8-bit ALU.(Arithmetic logical Unit)
• 8-bit internal data bus.
• 8-bit accumulator.
• 16-bit program counter.
• 16-bit stack pointer.
7. Basic features of 8085
• Requires a single +5V DC power supply.
• 16 address lines, it can access 64K bytes of memory.
• It can run at a maximum frequency of 3 MHz.
9. Basic Components in 8085
Register Section
ALU Section
Interrupt Control Section
Instruction register, Decoder and Control Section
Address and Address/Data buffer
Serial I/O control section
10. Register Section
• Temporary register:(W& Z register)
• General purpose register:(B,C,D,E,H&L register)
• Special purpose register
1. Stack Pointer
2. Instruction Register
3. Program counter
4. Accumulator
5. Flag Register
11. ALU Section
• Size: 8-bit
• Function: ALU performs the arithmetic operations
and logical operation. Like addition subtraction
multiplication division and ANDing, ORing, Ex-ORing
12. Instruction register, Decoder and
Control section
• Instruction registers(IR):-It is a 8-bit register. When
an instruction is fetched from memory then it is stored
in this register.
• Instruction Decoder:- Instruction decoder identifies
the instructions. It takes the information's
from instruction register and decodes the instruction to
be performed.
• Timing and Control Unit:-It provides timing and
control signal to the microprocessor to perform the
various operation
13. Interrupt control section
• There are 6 interrupt pins in this unit.
• Generally an external hardware is connected to these
pins. These pins provide interrupt signal sent by
external hardware to microprocessor and
microprocessor sends acknowledgement for receiving
the interrupt signal.
• Generally INTA is used for acknowledgement
14. Address and Address/Data Buffer
Address Buffer:
• It is 8-bit unidirectional buffer, Used For address line
• It is used to isolating the microprocessor from getting
loaded.
• It used to drive the higher order bus.
Address/Data Buffer:
• it is 8-bit bidirectional buffer, Used For address line.
• It is used to drive the lower order address and data
bus
15. Serial I/O control section
• There are two pins in this unit.
1. SID( serial in data)
2. SOD(serial out data)
• This unit is used for serial data communication.
1. SID: it is used to receive the data serially.
2. SOD: it is used to send the data serially.
• The data on these line is accepted or transferred
under software control by serial I/O control block.
