The document provides details about the 8085 microprocessor including its architecture, pin diagram, addressing modes, instruction set, timing diagram, applications, programming examples, advantages and disadvantages. It discusses the different units of the 8085 microprocessor such as the register unit, timing and control unit, arithmetic logic unit, and interrupt unit. Examples are provided to illustrate various instructions and addressing modes of the 8085 microprocessor.

1. 8085 MICROPROCESSOR
GROUP NUMBER :- 9
Group Members University Roll Numbers
Arkajit Biswas 12000317113
Arnab Bhattacharya 12000317112
Ardhendu Panja 12000317115
Amar Biswas 12000317130
Amit Kumar Nandi 12000317128
1

2. Contents
TOPICS SLIDE NO
1. Introduction ------------------------------ 3 - 6
2. Architecture ------------------------------ 7 - 14
3. Pin diagram ------------------------------ 15
4. Addressing mode ----------------------------- 16 - 18
5. Instructions set ------------------------------ 19 - 26
6. Timing diagram ------------------------------- 27 - 30
7. Applications -------------------------------- 31 - 32
8. Programming Examples ----------------------- 33 - 36
9. Advantages and Disadvantages -------------- 37-38
10. Conclusion --------------------------------- 39
11. References ---------------------------------- 40
2

3. Introduction to Microprocessor
• Microprocessor is a electronic chip, that functions as the central
processing unit of a real time system and a computer.
• For example: Washing machines, microwave ovens, mobile phones
etc.
• Its advance applications are: Radar, Satellites, flights.
3

4. Introduction to Microprocessor
(cond.)
• All microprocessors are use the basic concept of stored program execution.
Program or instructions are stored sequentially in the memory. In this way
microprocessors are used in embedded systems. Every microprocessor has
its own associated set of instructions. Instruction set of microprocessor is in
two forms one in mnemonic, which is comparatively easy to understand and
the other is binary machine code.
4

5. Introduction to ‘Intel 8085’
Microprocessor (cond.)
• The Intel 8085 is an 8-bit microprocessor introduced by Intel in
1977.
• The 8085 is based on von Neumann design. It is designed by using
NMOS technology. The “5” in the model number came from the fact
that the 8085 requires only a +5 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 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

6. Introduction to ‘Intel 8085’
Microprocessor (cond.)
• The 8085 has extensions to support new interrupts, with three
maskable 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). These 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

7. 8085 Microprocessor Architecture
7

8. Different units of 8085
Microprocessor
Register Unit
Timing and Control Unit
Arithmetic and Logical Unit
Interrupt Unit
Serial IO Unit
8

9. 1. Register Unit:
a) General Purpose Register
b) Special Purpose Register
The register unit consists of six general purpose data
registers and these are B, C, D, E, H and L two internal
registers W and Z.
o Program Counter
o Stack Pointer
o Increment or decrement counter
o Address buffer or data buffer
9

10. 2. Timing and Control Unit :
 This unit synchronizes all the microprocessor operation with
the clock and generate the control signals necessary for
communication between microprocessor and peripherals.
The timing and control units are used to control the internal as
well as external circuits. These are classified into four types
namely control units like 𝑅𝐷, 𝑊𝑅, ALE, READY, status units like
S0, S1, and IO/𝑀, DM like HLDA, and HOLD unit, RESET units
like RST-IN and RST-OUT.
10

11. 3. Arithmetic and Logical Unit:
The arithmetic and logic unit performs the computing
functions. It includes the accumulator, the temporary
register, the arithmetic and logic circuits and five flags.
The temporary registers are used to hold data during an
arithmetic/ logic operation. And the result is stored in the
accumulator and the flags (flip-flop) are set or reset
according to the result of the operation.
There are five flags in 8085 microprocessor. Sign Flag, Zero
Flag, Auxiliary Flag, Parity Flag and Carry Flag.
The bit positions reserved for these flags in the flag register are:
11

12. Arithmetic and Logical Unit (cond.) :
Sign Flag : After the execution of an arithmetic or logic
operation, if the D7 bit of the result is 1 , then Sign Flag is set.
Otherwise it is reset.
Zero Flag : The Zero Flag is set if the ALU operation results in 0,
and the flag is set if result is not 0.
Auxiliary Carry : In arithmetic operation, when a carry is
generated by digit D3 and passed on to digit D4 then Auxiliary
Carry flag is set, otherwise it is reset.
Parity Flag : After arithmetic or logical operation, if the result
has an even number of 1 then Parity Flag is set. If the result has
an odd number of 1 then it is reset.
Carry Flag : If an arithmetic operation results in a carry, then
the carry flag is set, otherwise it is reset. 12

13. 4. Interrupt Unit :
Hardware Interrupt :
 What is Interrupt ?
• Interrupt is a signal to the processor, generated by
hardware or software indicating an immediate
attention needed by an event.
Software Interrupt :
13

14. 5. Serial IO Unit :
The 8085 Microprocessor has two signals to
implement serial data transmission, Serial
Input Data (SID) AND Serial Output Data
(SOD).
In serial transmission data bits are sent over
a single line, one bit at a time, such as the
transmission over telephone line.
14

15. Pin Configuration of 8085 Microprocessor :
15

16. AddressingModes
The manner in which operands/data is given in a instruction is called addressing
mode. 8085 instructions can be classified in following addressing modes:--
 Register Addressing mode
 Data is provided through the registers .e.g. MOV, ADD, SUB, ANA, ORA, XRA
etc.
For Ex. MOV B, C move the content of register C to register B.
 Immediate Addressing mode
 Data is present in the instruction. Load the immediate data to the destination
provided. e.g. MVI, LXI,ADI, SUI, ANI, ORI etc.
For Ex. MVI A, 05H move the 05H in register A.
16

17. Addressing Modes (cond.)
 Direct Addressing mode
 Instructions have their operands in memory and the 16-bit memory
address is specified in the instruction
The address of the operand is given in the instruction. e.g. LDA, STA,
LHLD, SHLD etc.
For Ex. STA 7500H store the content of accumulator in the memory
location 7500 H.
 Indirect Addressing mode
In this address of the operand is specified by the register pair. The
address stored in the register pair points to memory location e.g.
LDAX, STAX etc.
For Ex. LDAX B;A in this case A get the value of address store in
register pair BC.
17

18. Addressing Modes (cond.)
Implicit or Implied Addressing mode
The operand is not specified in the instruction, specified within the opcode
itself.
Operand is supposed to be present in accumulator. e.g. CMA, CMC, STC etc.
For Ex: STC By using we can see carry flag.
18

19. Instruction Set
Since the 8085 is an 8-bit device it can have up to 28 (256) instructions.
However, the 8085 only uses 246 combinations that represent a
total of 74 instructions.
Most of the instructions have more than one format.
These instructions can be grouped into five different groups:
Data Transfer Operations
 Arithmetic Operations
Logic Operations
Branch Operations
Machine Control Operations
19

20. Instruction Set (cond.)
Data Transfer operation
 These operations simply COPY the data from the source to the
destination.
They transfer:
 Data between registers.[A,B,C,D,E,H,L]. For Ex: MOV B,C
 Data Byte to a register or memory location. For Ex: MVI B,25H
 Data between a memory location and a register. For Ex: LXI B,2000H
 Data between an I/O Device and the accumulator. For Ex:
LDAX,B[Accumulator get the value at address which store in BC register
pair]
 The data in the source is not changed.
 Data transfer instructions never affect the flag bits.
e.g. LDA, STA, MOV, LDAX, STAX, MVI, LXI etc.
20

21. Instruction Set (cond.)
Arithmetic Operation
 These instruction perform addition, subtraction and compare
operations.
These operations are always performed with accumulator as one of the
operands.
 The status of the result can be verified by the contents of the flag
register.
Addition: Any 8-bit number, or the contents of a register or the
contents of a memory location can be added to the contents of the
accumulator and the sum is stored in the accumulator. The instruction
DAD is an exception; it adds 16-bit data directly in register pairs.
Instruction Example- ADD, ADI. For Ex: ADD B[Value at register B added
with value at accumulator]
21

22. Instruction Set (cond.)
Subtraction - Any 8-bit number, or the contents of a register, or the
contents of a memory location can be subtracted from the contents
of the accumulator and the results stored in the accumulator.
Subtraction is done by 2’s compliment method and set carry flag to
indicate borrow.
Instruction example-SUB,SUI.
Increment/Decrement - The 8-bit contents of a register or a
memory location can be incremented or decrement by 1. Similarly,
the 16-bit contents of a register pair (such as BC) can be
incremented or decrement by 1. EX.INR,DCR 22

23. Instruction Set (cond.)
Logical Operation
Perform 8-bit basic logical operations with the content of the
accumulator
Logical instructions also modify the flag bits.
Op-codes for logical instructions include ANA, ANI, ORA, ORI, XRA,XRI, CMA,
CMC, RAL, RLC, RAR, RRC, CMP, CPI etc.
AND, OR Exclusive-OR - Any 8-bit number, or the contents of a register, or of
a memory location can be logically AND, Or, or Exclusive-OR with the
contents of the accumulator. The results are stored in the accumulator. For
Ex –ANA,ANI,ORA,ORI,XRA,XRI.
Compare- Any 8-bit number, or the contents of a register, or a memory
location can be compared for equality, greater than, or less than, with the
contents of the accumulator.
Complement - The contents of the accumulator can be complemented. 23

24. Instruction Set (cond.)
Logical Operation
Rotate- Each bit in the accumulator can be shifted either left or right to the next
position. There are four type of rotate :-
 Rotate Left With Carry(RLC)
 Rotate Right With Carry(RRC)
 Rotate Arithmetic Left(RAL)
 Rotate Arithmetic Right(RAR) 1. RLC
3.RAL
2. RRC
4. RAR
24

25. Instruction Set (cond.)
Branch Operation
These instructions are used to transfer the program control:
 To jump from one memory location to any other memory location
within a program
 From one program to another program called as a subroutine.
 Alters the sequence of program execution either conditionally or
unconditionally
Unconditional branch instructions- Transfer the program to the specified
label or address JMP unconditionally i.e. without satisfying any condition.
Conditional branch instructions -Transfer the program to the specified label
or
address when certain condition is satisfied.
JNC, JC, JNZ, JZ, JP, JM, JPE, JPO
25

26. Instruction Set (cond.)
 Machine Control Operation
These instructions include special instructions such as I/O data
transfer, perform machine related operation
 HLT – To halt the CPU
 NOP – To perform no operation
 SIM – To set the masking of hardware interrupts and serial output data
 RIM – To read the status of interrupt mask and serial input data
EI – Enable Interrupt
DI – Disable Interrupt
26

27. Timing diagram of 8085
microprocessor
To know the working of 8085 microprocessor, we should the timing
diagram of 8085 microprocessor. With help of timing diagram we
can easily calculate the execution time of instruction as well as
program. Before go to timing diagram of 8085 microprocessor we
should know some basic parameters to draw timing diagram of 8085
microprocessor. Those parameters are –
 Instruction Cycle
 Machine Cycle
 T-state
27

28. Timing diagram of 8085
microprocessor
• Instruction Cycle: Instruction cycle is the total time taken for
completing one execution
• Machine Cycle: Machine Cycle is the time required to complete one
operation such as accessing either the memory or an I/O device.
• T-state: T-state is the time corresponding to one clock period. It is a
basic unit used to calculate the time taken for execution of
instructions and programs in a processor.
28

29. Control Signals
• IO/M : IO/M signal indicate whether I/O or memory operation is
being carried out.
• S0 and S1 : S0 and S1 indicate the type of machine cycle in progress.
• ALE : ALE is indicates the availability of a valid address on the
multiplexed address / data lines. When it is high act as a address bus
and low act as data bus.
• RD^ : Read is an active low signal that indicates that data is to be
read from the selected memory or I/O device through data bus.
• WR^ : Write is an active low signal that indicates that data on the
data bus is to be write from the selected memory or I/O device.
29

30. Timing diagram
.
30

31. Applications of
Microprocessors
• Instrumentation: It has very wide applications in the field of
instrumentation in systems like in control panel of press printing
machine, digital kiosks, credit card processing, security systems etc.
It is also used in medical instruments like ECG (electronic
cardiogram) etc making the device smart.
• Entertainment: Microprocessors are also used in various gaming
consoles, DVD player, etc.
31

32. Applications of
Microprocessors (cond.)
• Communication: Microprocessors are being used in a wide range of
communication equipments like: in digital telephone sets, telephone
exchanges, in television, satellite communication, etc.
• Embedded Systems at Home: A number of modern device un the
home are microprocessor based i.e. camera; washing machines;
calculators; hi-fi systems; telephones; microwave ovens; burglar
alarms etc. The input are usually simple numeric keyboards, sensors,
buttons or while the output include lights, simple LCD screens
displays, motors and relays, LED’s, buzzers etc.
32

33. 8085 MICROPROCESSOR
PROGRAMMING EXAMPLES
33

34. 1.Writeaprogrammetoaddthecontentsoflocation2000Hand2001H.
Storethesumat2002Handthecarryat2003H.
Programme:
MVI C, 00H
LDA 2000H
MOV B,A
LDA 2001H
ADD B
JNC SKIP
INR C
SKIP: STA 2002H
MOV A,C
STA 2003H
HLT
2000 FF
2001 01
2002 00
2003 1
34

35. 2.Writeaprogrammetoperformblocktransferof10bytesfromlocation
2000Htolocation3000H.
Programme:
LXI B, 2000H
LXI D, 3000H
MVI L, 0AH
Back: LDAX B
STAX D
INX B
INX D
DCR L
JNZ Back
HLT
2000 50
2001 51
2002 52
2003 53
2004 54
2005 55
2006 56
2007 57
2008 58
2009 59
3000 50
3001 51
3002 52
3003 53
3004 54
3005 55
3006 56
3007 57
3008 58
3009 59
35

36. 3.Writeaprogramtoperforminvertedblocktransferof10bytesfrom
locations 2000H to 3000H.
Programme:
LXI B, 2000H
LXI D, 3009H
MVI L, 0AH
Back: LDAX B
STAX D
INX B
DCX D
DCR L
JNZ Back
HLT
2000 50
2001 51
2002 52
2003 53
2004 54
2005 55
2006 56
2007 57
2008 58
2009 59
3000 59
3001 58
3002 57
3003 56
3004 55
3005 54
3006 53
3007 52
3008 51
3009 50

37. ADVANTAGES
1. The 8085 microprocessor can quickly move data between
the various memory locations.
2. This processor can be programmed to execute a number of
tasks.
3. Another advantage of this processor is its speed, which is
measured in hertz. For instance, a microprocessor with 3
GHz is capable of performing 3 billion tasks per second.
37

38. DISADVANTAGES
1. The 8085 microprocessor might get overheated.
2. This microprocessor does not have any internal peripheral like
ROM, RAM and other I/O devices.
3. In this processor, due to limited 8 bit size of all the registers,
we can store limited data bytes in the microprocessor
memory.
4. Flag register has limited flags.
38

39. Conclusion
• The 8085 processor was used in a few early personal computers,
produced from 1977 to mid 1980’s.
• But the size (memory) of the microprocessor is not sufficient. Also it
has low speed. And to solve this problems better quality
microprocessors have been developed with time with greater bit
processing capability (32 and 64 bit) along with huge number of
modifications.
• Now a days, in many engineering institutes the 8085 processor is
used in introductory microprocessor courses.
39

40. References
• http://www.intel.com/ pressroom/kits/quickerfyr.htm#1976
• www.polytechnichub.com
• https://en.wikipedia.org/wiki/Intel_8085
• http://scanftree.com/microprocessor/Evolution-and-Classification-
of-Microprocessors
• http://www.daenotes.com/electronics/digital-electronics/Intel-
8085-8-bit-microprocessor
• www.Engineering.nbcafe.in
40

41. Thank You
41