It is useful for micro processor and controller

1. Micro-Controllers And
Interfacing(MCI)
Unit-I
Presented by
R. Padmasree
Assistant Prof.
Department of ECE

2. Contents:-
 Mini Computers.
 Micro-processors.
 Micro-controllers.
 Digital signal Processors.
 CISC Vs RISC Processors.
 ARM Processors.
 Overview of 8085 Microprocessor.

3. Classification of Computers
Computers are classified into 4 types based on size they are
Super Computer
Main frame Computer
Micro computer
Mini Computer

4. Supercomputer :-
Supercomputers were introduced in the
1960s
A supercomputer is a computer with a
high level of performance as compared
to a general-purpose computer.
Supercomputers are used for data-
intensive and computation-heavy
scientific and engineering purposes such
as quantum mechanics, weather
forecasting, oil and gas exploration,
molecular modeling, physical
simulations, aerodynamics, nuclear
fusion research and cryptanalysis.

5. Main Frame Computers :-
 Mainframe computers are discovered in
1950’s.
 A mainframe computer is large but not as
large as a supercomputer.
 Mainframes are high-performance computers
with large amounts of memory and
processors that process billions of simple
calculations and transactions in real time.
 Large organizations with high-data
processing or storage needs to use a
mainframe computer. Airlines, banks,
retailers, e-commerce companies,
government agencies and IT service
providers are all examples of entities that
might use a mainframe computer.

6. Micro Computer :-
 A microcomputer is a small, relatively
inexpensive computer having a central
processing unit(CPU) made out of
a microprocessor
 The computer also includes memory
and input/output(I/O) circuitry together
mounted on a printed circuit board(PCB).
 Microcomputers became popular in the
1970s and 1980s with the advent of
increasingly powerful microprocessors.

7. Mini Computers :-
 These are first developed in the 1960s and early 1970s.
 A Minicomputer is a type of computer that possesses most of the features
and capabilities of a large computer but is smaller in physical size.
 Minicomputers may contain one or more processors, support
multiprocessing and tasking, and are generally resilient to high
workloads.
 Although they are smaller than mainframe or supercomputers,
minicomputers are more powerful than personal computers and
workstations.
 Minicomputers were used for scientific and engineering computations,
business transaction processing, file handling, and database management.
 Some examples of Mini Computers are Tablet PCs, Smartphones,
Notebooks, Touch Screen pads, Desktop Mini Computers.

8. Features of Mini Computers
The Key features of Mini Computer are
 CPU
 GPU
 Memory
 Storage
 I/O Ports
 Operating System (OS)
 Mounting and Organization Accessories

9. Advantages and Dis-advantages of Mini Computer
Advantages :-
 Minicomputers are easy to maintain and use.
 Minicomputers are smaller in size so that they can be placed anywhere.
 Minicomputers are portable.
 Minicomputers are fast.
 Minicomputers are reliable.
Dis-Advantages :-
 Less Storage.
 Small Screen size.
 Keyboard size.
 All the models of mini computer comes with integrated graphics instead
of a dedicated GPU.

10. Micro-Processors
 Microprocessor is an Integrated
Circuit(IC) that contains all the
functions of a central processing
unit of a computer.
 It performs ALU operations(8
bit/16bit/32bit…)
 The four main functions of
Microprocessor are
 Fetch
 Decode
 Execute
 Write back

11. System Bus of Micro-Processor :-
The functional components usually use a bus architecture for communication and
different types of Buses used are:
Address Bus:-The address bus is used to communicate the address of the given
data and instructions.
Data Bus:-The data bus is used to communicate the
data from one part to another.
Control Bus:-The control bus is used to control the
signals between different devices.
Hence these functional components communicate
through this bus architecture

12. Memory of Micro-processor
The parts of memory are:
Primary Memory:- This is the internal memory that stores the data and
instructions of the CPU. It is volatile in nature (data is lost when the power is
disconnected).The primary memory has two types:
RAM (Random Access Memory)
As per the name, data can be accessed randomly and quickly.
ROM (Read Only Memory)
As per the name, we can only read data and cannot write (store) to it.
Secondary Memory:-As the primary memory is volatile therefore, we need
some devices to store the data permanently so we use some external storage
devices for this purpose which we name as the secondary memory. Some
examples: CD, DVD, etc.

13. Characteristics of Micro-Processors
Three important characteristics of a Microprocessor are as follows:
 Clock Speed
 Word Size
 Instruction Set
Clock speed :- The speed at which a microprocessor can execute the
instructions is called the clock speed. Basically clock speed is the number of
cycles that the processor executes per second. We measure it in MHz(Mega
Hertz) or GHz (Giga Hertz).
Word size :- It is the number of bits that a processor can process in a single
instruction.
Instruction Set:-An instruction is basically a command which tells the
computer to operate on some piece of data.

14. TYPES OF MICROPROCESSORS

15. Reduced Instruction Set Computer(RISC) Processor
RISC Processor is designed to reduce the execution time by
simplifying the instruction set of the computer.
Using RISC processors, each instruction requires only one clock
cycle to execute results in uniform execution time. This reduces
the efficiency as there are more lines of code, hence more RAM is
needed to store the instructions.
The compiler also has to work more to convert high-level
language instructions into machine code.

16. Data Cache :- It is a
process that stores
multiple copies of data
or files in a temporary
storage location so that
they can be accessed
faster.
Instruction Cache:- It is
a process that stores
multiple copies of
instructions in a
temporary storage
location so that they can
be accessed faster.

17. Characteristics of RISC
The major characteristics of a RISC processor are as follows −
It consists of simple instructions.
It supports various data-type formats.(Integer, Float, Boolean,
Character……)
It utilizes simple addressing modes and fixed length instructions for
pipelining (the process of storing and prioritizing computer instructions
that the processor executes).
It supports register to use in any context.
One cycle execution time.
“LOAD” and “STORE” instructions are used to access the memory
location.
It consists of larger number of registers.
It consists of less number of transistors.

18. The most common RISC microprocessors are -----
 Alpha – 64 bit RISC Processor.
 ARC(Argonaut RISC Core) - 32 bit & 64 bit.
 ARM(Advanced RISC Machine) -32 bit & 64 bit.
 AVR ( Alf and Vegard's RISC) - 8-bit Microcontroller
 MIPS(Microprocessor without Interlocked Pipelined Stages) – 32
bit & later developed 64 bit.
 PA-RISC(Precision Architecture) - 32 bit & later developed 64 bit.
 PIC(Peripheral interface controller) – 16 bit controller
 Power Architecture – 64 bit processor
 SPARC(Scalable Processor Architecture) - 32 bit & 64 bit

19. Complex Instruction Set Computer (CISC) PROCESSOR
CISC processor is designed to minimize the number of instructions
per program, ignoring the number of cycles per instruction.
The emphasis is on building complex instructions directly into the
hardware.
The compiler has to do very little work to translate a high-level
language into assembly level language/machine code because the
length of the code is relatively short, so very little RAM is required
to store the instructions.
Some of the CISC Processors are −
IBM 370/168(3G Computers)
VAX 11/780(virtual address extension)
Intel XX86(8086 family)

20.  CISC architecture is
designed to decrease the
memory cost because
more storage is needed in
larger programs resulting
in higher memory cost.
To resolve this, the
number of instructions per
program can be reduced
by embedding the number
of operations in a single
instruction.

21. Characteristics of CISC
 Variety of addressing modes.
 Larger number of instructions.
 Variable length of instruction formats.
 Several cycles may be required to execute one instruction.
 Instruction-decoding logic is complex.
 One instruction is required to support multiple addressing
modes.

22. CISC RISC
Larger set of instructions. Easy to program Smaller set of Instructions. Difficult to
program.
Simpler design of compiler, considering larger
set of instructions.
Complex design of compiler.
Many addressing modes causing complex
instruction formats.
Few addressing modes, fix instruction format.
Instruction length is variable. Instruction length varies.
Higher clock cycles per second. Low clock cycle per second.
Emphasis is on hardware. Emphasis is on software.
Control unit implements large instruction set
using micro-program unit.
Each instruction is to be executed by
hardware.
Slower execution, as instructions are to be
read from memory and decoded by the
decoder unit.
Faster execution, as each instruction is to be
executed by hardware.
Pipelining is not possible. Pipelining of instructions is possible,
considering single clock cycle

23. Special Processors
These are the processors which are designed for some special purposes,
they are
Coprocessor :- It is a specially designed microprocessor, which can
handle its particular function many times faster than the ordinary
microprocessor.
E.g. :- − Math Coprocessor, Some Intel math-coprocessors are −
8087used with 8086.
Input/output Processor :-It is a specially designed microprocessor having
a local memory of its own, which is used to control I/O devices with
minimum CPU involvement.
E.g. :− DMA (direct Memory Access) controller
Keyboard/mouse controller
Graphic display controller

24. Transputer (Transistor Computer) :-It is a specially designed
microprocessor with its own local memory and having links to connect
one transputer to another transputer for inter-processor communications,
It was first designed in 1980.
A transputer can be used as a single processor system or can be connected
to external links, which reduces the construction cost and increases the
performance.
E.g. :- − 16-bit T212, 32-bit T425, the floating point (T800, T805 &
T9000) processors.
DSP (Digital Signal Processor) :-It is specially designed to process the
analog signals into a digital form. This is done by sampling the voltage
level at regular time intervals and converting the voltage at that instant
into a digital form. This process is performed by a circuit called an
analogue to digital converter, A to D converter or ADC.

26. A DSP contains the following components -
Program Memory − It stores the programs that DSP will use to process
data.
Data Memory − It stores the information to be processed.
Compute Engine − It performs the mathematical processing, accessing
the program from the program memory and the data from the data
memory.
Input/output − It connects to the outside world.
Its applications are −
Sound and music synthesis.
Audio and video compression.
Video signal processing.
2D and 3d graphics acceleration

27. 8085 MICROPROCESSOR
PIN Diagram & Description

28. Power supply and clock signals:-
VCC – Pin number 40 denotes VCC, and an external power supply of + 5 V is
provided at this pin.
VSS – Its pin number is 20. This pin shows the grounded connection of the
Microprocessor.
X1 and X2 – These are represented by pin number 1 and 2 respectively in the pin
configuration. These 2 pins are connected with a crystal or LC network to maintain
the internal frequency of the clock generator.
CLK (OUT) – It is the 37th pin of the 8085 IC and acts as the system clock that
keeps the record of time duration required by each operation to get completed.
Address Bus:-- A8 to A15
The address bus has 16 lines i.e.; it can carry 16 bits at a time. However, out of 16, 8
are multiplexed with the data bus and the leftover 8 are separately shown by pin
number 21 to 28 in the pin configuration.
These are used to carry the address of data and instruction from the processor to the
memory location and is unidirectional in nature. These are denoted by A8 to A15 that
represents the 8 MSB of the memory location or input-output address.

29. Data Bus with multiplexed address bus :--(AD0 to AD7)
This category also contains 8 pins shown by pin number 12 to 19.
The size of the data bus of the 8085 microprocessor is 8 bits.
The address bus is denoted by A whereas the data bus is denoted by D. The pin
configuration denotes the lower order multiplexed address and data bus bits
from AD0 to AD7.
The address bus contains the address of the desired memory location from where
the data or instruction is to be fetched. While the data bus contains the data or
instruction that is needed to be fetched from the memory.
Serial I/O ports : --
It has basically 2 pins.
SID – SID denotes serial input data pin and its pin is numbered as 5. With this
pin, data is serially fed to the processor directly through the input devices.
SOD – SOD denotes serial output data pin and its pin number is 4, in the pin
configuration of 8085. Once the data is processed in the microprocessor then this
pin represents bit by bit results at the output devices.

30. Control and status signals :--
Basically, 6 pins of the pin configuration are used by control and status signals.
ALE – ALE stands for address latch enable and is pin number 30 in the
configuration. This pin gets enabled at the time when the address is present at the
multiplexed address and data bus. Otherwise, it gets disabled showing the absence
of an address on the bus.
RD – This pin is numbered 32 in the configuration and a low signal in this pin
shows the read operation either from I/O devices or from the memory unit. Thereby
indicating that the data bus is now in a state or position to accept the data from the
memory or I/O devices.
WR – It is the 31st pin in the pin diagram and a low signal in this pin represents the
write operation at the memory or I/O devices. This indicates that the data present in
the data bus is to be written into the desired memory address or I/O device by the
processor.
IO/M – It is pin number 34 and indicates the selection of a memory address or
input-output device. This shows whether the read/write operation is to be carried
out at the memory location or at the I/O device.

31. The low signal at this pin shows that operation is performing over memory
location. As against, a high signal at this pin represents the operation at I/O
device.
S0 and S1 – The pins S0 and S1 represent the status signal at pin number 29 and
33 respectively. These signals show the type of recent operation of the
microprocessor. The table below represents the status of the data bus under
different conditions:
IO/𝑴 𝑺𝟏 𝑺𝟎 Operation
0/1 0 0 HALT
0 0 1 Memory write
0 1 0 Memory read
0 1 1 Opcode fetch
1 0 1 I/O write
1 1 0 I/O read
1 1 1 Interrupt Acknowledgement

32. Interrupts and Externally generated signals:--
Interrupts are the signals that are generated to break the sequence of an ongoing
operation. When an interrupt signal is generated then CPU immediately stops its
recent task under operation and switches to some other program known as interrupt
service routine (ISR),after handling ISR, the CPU gets back to its main program for
execution.
5 types of interrupts are shown by 5 different pins from pin number 6 to 10. These
pins are used to manage the interrupt.
Basically, there exist 2 types of interrupts:
Maskable Interrupt (Can be ignored) and Non- maskable interrupt (cannot be
ignored)
Out of the 5 major interrupts 4 are the maskable interrupts. These are INTR,
RST5.5, RST6.5, RST7.5 and are easily manageable interrupts.
However, TRAP is a non-maskable interrupt and holds the topmost priority among
all interrupts in the 8085 microprocessor.

33. RESET IN – It is pin number 36 in the pin diagram. An active low signal at this
pin resets the PC of the microprocessor to 0. Or we can say, after resetting the PC
holds its initial memory address.
RESET OUT – It is the 3rd pin in the pin diagram. This pin generates a signal to
provide information about the resetting of the microprocessor. Also, we can say
that once a processor is reset then all the connected devices must also be reset.
So, enabling this signal shows the resetting of the interconnected devices.
INTA: It is the 11th pin of the 8085 pin configuration. A signal at this pin
acknowledges the generated interrupt.
Direct Memory Access (DMA) :--
We are aware of the fact that memory and I/O devices are connected with each
other by the microprocessor. So, the intermediator i.e., CPU manages the data
transfer between the input-output device, it has 2 pins.
HOLD
HLDA

34. HOLD – This signal is generated at pin number 39. This pin generates a signal to
notify the processor that more than one request is present to access the data and
address bus.
When this signal gets enabled, the CPU frees the bus after completion of the recent
operation. Once the hold signal gets disabled, the processor can access the bus
again.
HLDA -This signal is generated at pin number 38. This signal is enabled at the time
when the processor gets HOLD signal and it releases HLDA i.e., hold acknowledge
signal. In order to show that the multiple requests are kept on hold and will be
considered once the bus gets free after the recent operation.
After the disabling of hold request, the HLDA signal becomes low.
READY -This is the 35th numbered pin in the pin diagram that maintains
synchronization between the processor and peripherals, memory. It is clear that a
microprocessor has a much faster response than peripherals and memory.
So, this pin is enabled when the processor as well as the peripherals and memory
both become ready to begin the next operation.
In the case when the READY pin is disabled, then the microprocessor is in the
WAIT state.

35. Architecture of 8085
The microprocessor 8085 is the first successful processor used
in practical applications, It is designed by Intel in 1977.
This microprocessor is manufactured using NMOS Technology.
The 8085 microprocessor is used in different devices and
projects such as calculators, video game players, embedded
systems, automation systems, digital controllers, smartwatches,
etc.
8085 is an 8-bit general purpose microprocessor with a 3.2 MHz
single-phase clock.

37. Registers:--
These are nothing but set of flip flops. These are basically used to hold (store) the
data they are of three types general purpose, temporary and Special purpose
registers
General purpose registers – 8085 microprocessors contain 6 general purpose
registers that are present inside the microprocessor and stores 8-bit data in order to
execute a program. These general purpose registers are B, C, D, E, H and L.
These registers can be combined to form pairs – BC, DE and HL in order to execute
the 16-bit operation. These are programmable registers, that means these registers
are accessed by the programmer to insert and transfer the data by making use of
instructions.
Temporary registers --- These registers are used by the ALU to store the data
on temporary basis and these are not accessed by the programmer. These are of 2
types:
Temporary data register – It is an 8-bit register that holds the operand and provides
it to the ALU for program execution. Also, the immediate results are stored by the
ALU in this register.

38. W and Z register – These registers are also used to hold the temporary values. It is
used by the control section of the microprocessor so as to store the data during
operations.
Special Purpose registers –
Program Counter (PC): It is a 16-bit register which is used to store the memory
address of the next instruction to be .This register is used by the microprocessor to
line up the instructions that are to be executed in a sequential manner.
Stack Pointer (SP): It is also a 16-bit register and is a part of memory. The data is
stored in the stack in serial format and stack pointer generally stores the address of
the last data element stored in the stack. Thus the stack is based on LIFO.
Whenever a new data is added in the stack, then the stack pointer starts pointing
towards the very next memory location.
As against, when a data element is removed from the stack, then the stack pointer
points to previous occupied memory location.
Increment/Decrement Register :-- It is used to increment or decrement the
contents of 16-bit registers

39. Accumulator: It is an 8-bit register that stores the result of the operation
performed by the ALU. It is also known as register A.
Flags: Flag register basically holds the status of the current result
generated by the ALU and not the actually generated result. Thus we
can say it is used to test the data conditions.
The flag register bits are carry flag, parity flag, Auxiliary carry flag,
zero flag and sign flag

40. Arithmetic and logic unit
As the name suggests, it performs arithmetic and
logical operations like Addition, Subtraction, AND, OR, etc. on 8-bit
data.
Instruction register :-
It is used to store the set of instructions
Instruction Decoder and Machine Cycle Encoder :
This accepts a bit pattern (OPCODE) from instruction
register, decodes it and gives the decoded information to control logic.

41. Microcontroller
Microcontroller (also called Embedded Computer) is a mini computer,
embedded in a compact IC(Integrated Circuit) chip, contains on-chip
processor(one or more), memory(i.e. RAM, ROM, EEPROM etc.) &
programmable I/O Ports(used for multiple functions).
Microcontroller's Architecture consists of—
 CPU(Central Processing Unit).
 ROM(Read-only memory).
 RAM(Random-access memory).
 EEPROM(Electrically-Erasable Programmable Read-only memory).
 Ports I/O.
 Timers.
 Interrupts.

43. CPU (Central Processing Unit)
It is the heart of the Microcontroller
that mainly comprises of an
Arithmetic Logic Unit (ALU) and a
Control Unit (CU) and other
important components. The CPU is
the primary device in communicating
with peripheral devices like Memory,
Input and Output.
ALU or Arithmetic Logic Unit, as the
name suggests, performs the
Arithmetical and Logical Operations.
CU or Control Unit is responsible for
timing of the communication process
between CPU and its peripherals

44. Interrupt control logic :-To generate interrupts signals which tells
the CPU to pause its current task and start executing another set of
predefined activities.
Timer/Counter :- They can be used as timers or as event counters,
When they work as a timer to generate a time delay or as counter to
count events happening outside the microcontroller.
I/O Ports :- It is a function for exchanging data and signals between
external devices and a microcontroller.
EEPROM:--It's only an array of memory bits with an addressing
scheme that allows an controller to read from or write data to it.
Stack :-- The stack is a section of a RAM used by the CPU to store
information such as data or memory address on temporary basis.

45. Differences between Microprocessor and Microcontroller
Microprocessor Microcontroller
Microprocessor acts as a heart of computer system. Microcontroller acts as a heart of embedded system.
It is a processor in which memory and I/O output
component is connected externally.
It is a controlling device in which memory and I/O
output component is present internally.
Since memory and I/O output is to be connected
externally. Therefore the circuit is more complex and
consumes more power.
Since on chip memory and I/O output component is
available. Therefore the circuit is less complex and
consumes less power.
Microprocessor has less number of registers.
Therefore most of the operations are memory based.
Microcontroller has more number of registers.
Therefore a program is easier to write.
A microprocessor having a zero status flag. A microcontroller has no zero flag.
It is mainly used in personal computers. It is mainly used in washing machines, air
conditioners etc.
Cost is high and speed is low Cost is low and speed is high

46. Advanced RISC Machine (ARM7) Processor

47. It is a RISC Processor which obeys Von Neumann architecture.
It has 32 bit data and address bus
Memory of ARM7 Processor is 4GB.
It contains 37(31 General purpose + 6 status ) registers.
It contains Barrel shifter which left shifts or right shifts data by any
no. of bits position.
It contains 32*8 bit multiplier.
32 bit ALU.
Address register --- holds the address of instruction that is to be
fetched.
Instruction decoder and control logic – enables interfacing
peripherals to processor

50. It is clear from the diagram that only the BIU has a direct link with the
memory. This memory can be directly accessed either by the segment
registers, the Instruction Pointer (IP) or the Instruction Queue for
fetching up the instructions.
These instructions are sent in the Control Unit for execution. The control
unit takes the help of General Purpose registers, Index registers and
Pointers, operands, flags and the most important, the Arithmetic Logic
Unit (ALU). All these are part of the Execution Unit.
Bus Interface Unit (BIU)
The Instruction Queue contains the set of instruction which is to be
executed. To make the processing faster, the 8086 pre-fetches up to 6
instructions in advance and stores them in the Instruction queue. So,
whenever one instruction completes its execution, the control unit need
not wait for the next instruction to be fetched and then brought for
execution because this job is already done and the next instruction that is
to be executed is ready in the Instruction queue.

51. Segment register − BIU has 4 segment registers i.e. CS, DS, SS& ES.
It holds the addresses of instructions and data in memory, which are
used by the processor to access memory locations.
CS − It stands for Code Segment. It is used for addressing a memory
location in the code segment of the memory, where the executable
program is stored.
DS − It stands for Data Segment. It consists of data used by the
program and is accessed in the data segment by an offset address or the
content of other register that holds the offset address.
SS − It stands for Stack Segment. It handles memory to store data and
addresses during execution.
ES − It stands for Extra Segment. ES is additional data segment, which
is used by the string to hold the extra destination data.
Instruction pointer − It is a 16-bit register used to hold the address of
the next instruction to be executed.

52. General purpose register
There are 8 general purpose registers, i.e., AH, AL, BH, BL, CH, CL,
DH, and DL. These registers can be used individually to store 8-bit
data and can be used in pairs to store 16bit data. The valid register pairs
are AH and AL, BH and BL, CH and CL, and DH and DL. It is referred
to the AX, BX, CX, and DX respectively.
AX register − It is also known as accumulator register. It is used to
store operands for arithmetic operations.
BX register − It is used as a base register. It is used to store the
starting base address of the memory area within the data segment.
CX register − It is referred to as counter. It is used in loop
instruction to store the loop counter.
DX register − This register is used to hold I/O port address for I/O
instruction

53. Pointers and Index Registers :-
Stack pointer :-It stores the memory address of the last data element
added to the stack or, in some cases, the first available address in the
stack.
Base pointer :- It points to data in stack segment.
Source index registers & Destination index registers :-
As the name follows, SI is always pointed to the source data addresses
and DI is always pointed to the destination. This is usually used to
move a block of data, such as records (or structures) and arrays. These
register is commonly coupled with DS and ES.

55. Conditional Flags :-It represents the result of the last arithmetic or logical
instruction executed, they are carry flag, zero flag, parity flag, sign flag,
Auxiliary carry flag and overflow flag.
Control Flags
Control flags controls the operations of the execution unit. Following is the
list of control flags −
Trap flag − It is used for single step control and allows the user to execute
one instruction at a time for debugging. If it is set, then the program can be
run in a single step mode.
Interrupt flag − It is an interrupt enable/disable flag, i.e. used to
allow/prohibit the interruption of a program. It is set to 1 for interrupt
enabled condition and set to 0 for interrupt disabled condition.
Direction flag − It is used in string operation. As the name suggests when it
is set then string bytes are accessed from the higher memory address to the
lower memory address and vice-a-versa.