Download - Microprocessor Notes 1
-
8/20/2019 Microprocessor Notes 1
1/15
A Microprocessor-based systemThe block diagram of a microprocessor-based system:
>>In order for the microprocessor to function as a programmable
device, it must work in a complete system comprising of three
components : microprocessor, memory and input/output. This
system is called microprocessor‐ based system or microcomputer
system. These three components will work together or interact
with each other to perform a given task.
System Buses
>>The three components of the microcomputer system is
connected by three busses, also known as system bus.
>>These busses is used to transfer information (data) internally
and externally to the microprocessor.
Address Bus
>>It carries the address of a unique memory or input/output
(I/O) device
>>The address bus is ʹunidirectional ́, over which the
microprocessor sends an address code to the memory or
input/output. The size (width) of the address bus is specified by
the number of bits it can handle.
-
8/20/2019 Microprocessor Notes 1
2/15
>>The more bits there are in the address bus, the more memory
locations a microprocessor can access. A 16 bit address bus is
capable of addressing 65,536 (64K) addresses.
Data Bus
>> The data bus carries data stored in memory (or an I/O device)
to the CPU or from the CPU to the memory (or I/O device)
>> The data bus is ʹbi‐directional ́, on which data or instruction
codes are transferred into the microprocessor or on which the
result of an operation or computation is sent out from the
microprocessor to the memory or input/ output.
>>Depending on the particular microprocessor, the data bus can
handle 8 bit or 16 bit data.
Control Bus
>>a collection of control signals that coordinate and synchronize
the whole system
>>The control bus is used by the microprocessor to send out or
receive timing and control signals in order to coordinate and
regulate its operation and to communicate with other devices, i.e.
memory or input/output.
-
8/20/2019 Microprocessor Notes 1
3/15
CPU
>> Microprocessor is also called Central Processing Unit (CPU)
since it is the functional centre of the computer system and it is
used to process data.
>> Microprocessor: A multipurpose , programmable logic device (IC) that reads
binary instructions from a storage device called memory , accepts
binary data as input and processes data according to those
instructions, and provide results as output.
(A multipurpose device: it can be used to perform various
sophisticated computing tasks or functions, as well as simple
tasks.
A programmable device: it can be instructed to perform given
tasks within its capability.)
>> Microprocessor is designed to understand and execute many
binary instructions.
-
8/20/2019 Microprocessor Notes 1
4/15
Memory
>>The memory in a computer system stores the data and instructions of
the programs.
>>Memory is the term used to the various storage devices in
which are used to store the programs and data for the
microprocessor.
>>These storage devices are made of semiconductor devices, and
also known as Primary Storage Devices.
Input/Output >>The input/output unit allows the microprocessor to
communicate with the outside world, either to receive or to send
data.
>>Most of the time, the input/output unit will also act as an
interface for the microprocessor, that is to convert the data into a
suitable format for the microprocessor.
>>Data can
be
in
the
form
of
parallel
(8
bit)
or
serial
format
(single
line).
>>Input devices are devices that input data or send data to the
computer. Input devices are such as keyboard, punched card
readers, sensors, switches, etc.
-
8/20/2019 Microprocessor Notes 1
5/15
>>Output devices are devices that output data or perform various
operations under the control of the CPU. Output devices are
LEDs, 7‐segment display unit, speaker, CRT, printer, digital
speedometer, fuel
injectors,
etc.
Inside The Microprocessor>>Internally, the microprocessor is made up of 3 main units.
The Arithmetic/Logic Unit (ALU)
The Control Unit.
Register Array>> Microprocessor:
A multipurpose , programmable logic device (IC) that reads
binary instructions from a storage device called memory , accepts
binary data as input and processes data according to those
instructions, and
provide
results
as
output.
(A multipurpose device: it can be used to perform various
sophisticated computing tasks or functions, as well as simple
tasks.
-
8/20/2019 Microprocessor Notes 1
6/15
A programmable device: it can be instructed to perform given
tasks within its capability.)
>> Microprocessor is designed to understand and execute many
binary instructions.
>> Microprocessor is also called Central Processing Unit (CPU)
since it is the functional centre of the computer system and it is
used to process data.
Block diagram of a typical CPU
Register Section >>An array of registers for holding data while it is being
manipulated.
-
8/20/2019 Microprocessor Notes 1
7/15
>>The register section/array consists completely of circuitry used
to temporarily store data or program codes until they are sent to
the ALU or to the control section or to memory.
>>The number
of
registers
are
different
for
any
particular
CPU,and the more >>register a CPU have will result in easier
programming tasks.
Arithmetic and Logic Unit (ALU)
>>This section, under the control of control section carries out the
actual processing of data , normally describe as data
manipulation. This consists largely of arithmetic operations
(ADDition, SUBtraction, INCrementing, DECrementing etc) and logical operations (ANDing, ORing, XORing, NOTing etc).
>>The ALU carries out these operations in the following manner :‐
>>stores data fetched from memory or I/O in the registers
>>fetches this data as needed from the registers and/or from
relevant accumulators
>>send this data either to its arithmetic circuitry or logical
circuitry, where necessary, where the necessary arithmetic or logical operations are carried out
>>send results of its arithmetic or logical operation to
relevant accumulator, to the memory, or to the I/O
interfaces.
Control Unit
>>The control section/unit is the part of the microcomputer that
controls its basic operations. It is made up of the control signal generating circuitry (clock) and the command (instruction)
decoder.
>>The control section fetches pre‐programmed instructions from
memory (op‐code fetch cycle) as needed and temporarily stores
-
8/20/2019 Microprocessor Notes 1
8/15
them in the command register (also known as Instruction
Register IR).
>>These instructions are then decoded by the operation decoder
(decode cycle) ,
which
sends
control
signals
to
the
relevant
parts of the microcomputer system (via the system busses) to
cause them to carry out the required operation (execute cycle)
>>The timing with which these control signals are generated is
determined by the clock. The number of T‐states tells the
time taken for the CPU to execute that particular instruction.
CPU structure
The main functions are>>data transfer
>>arithmetic and logic operations
>>decision making (instructional flow control)
>>The register array consists of at least one accumulator, program counter
and stack pointer.
>>The control unit controls all the operations in a CPU and basically it
puts the CPU in one of the fetch and execution phases.
>>The major
types
of
operations
controlled
by
the
control
signals:
>> sending of data from one part of the microcomputer to
another (read or write cycle)
>>inputting and outputting of data to/from the
microcomputer (I/O read or write cycle)
>>Arithmetic and Logic calculations.
>>Halting of computer instructions.
>>Jumping to
another
instruction
during
running
(execution)
of a program.
-
8/20/2019 Microprocessor Notes 1
9/15
Operation of the CPU
Fetch cycle (phase):
The CPU puts the address of the instruction to be executed on
the address bus. The address information comes from the program
counter (PC) maintained by the control unit.
The control bus holds the information for reading the memory
location and the data bus holds the instruction from the memory which is
stored into the instruction register (IR)
PC is updated to point to the next instruction.
Execute cycle (phase):
Instruction in the IR is decoded
The required data transfer and the required logical and
arithmetic operation are performed
The result is written back either to one of the registers or
memory or I/O device
Common operations performed in ALU :
addition, subtraction,logical AND, OR, XOR, NOT
increment, decrement, shift, clear, etc.
-
8/20/2019 Microprocessor Notes 1
10/15
Microcomputer
CPU on a single IC microprocessor (µP).
The terms CPU, µP and MPU (microprocessor unit) are
synonymous
CPU is the combination of the ALU and control unit of anycomputer.
When the CPU is a single IC; it is called a µP and is also referred
to as the MPU.
When the MPU is connected to memory and I/O, the arrangement
becomes a MICROCOMPUTER.
Many different MPUs are produced by many different IC vendors (e.g.,
Intel, Motorola, Texas Instruments, Zilog, National Semiconductors,
etc.).
Major differences are inword size,
the number and types of instructions that can be performed,
the types of external control signals available,
the amount of memory that can be addressed.
Organization of a microprocessor-based system
Let’s expand the picture a bit.
Microcontroller
-
8/20/2019 Microprocessor Notes 1
11/15
A microcontroller unit (MCU) contains an MPU, memory, and
I/O circuitry on a single chip.
Such a chip can perform control operations without the need for
any external circuitry.
e.g. Motorola MC68HC11 (also a microprocessor in the expandedmultiplexed mode) e.g.
Intel 8051
Microprocessors vs microcontrollers
Microprocessor
>>Microprocessors: high performance, general purpose “brains” for PCs
and workstations
>>Instruction decode and control, arithmetic/logic operations, registers,
timing, external control>>Includes memory management unit, lots of cache
>>Performance is the most important feature (cost is important, but
secondary)
>>Used mainly in desktop machines
Microcontroller
>>Microcontrollers: devices with high levels of integration for
embedded control
>>Microprocessor functions plus on-chip memory and peripheralfunctions (e.g. ports, timers)
>>Integrated RAM and ROM, no cache
>>Includes lots of peripherals
>>Used mainly in “embedded” applications and often involves real-time
control
>>Important features include: low cost, low power consumption, number
of integrated peripherals, interrupt response time, amount of RAM and
ROM
-
8/20/2019 Microprocessor Notes 1
12/15
The block diagram of a microcontroller
Memory >>The memory in a computer system stores the data and instructions of
the programs.
>>Memory stores information such as instructions and data in binary
format (0 and 1). It provides this information to the microprocessor
whenever it is needed.
Main memory typesThe semiconductor memory is of 2 types that is Read Only
Memory (ROM) and Read Write Memory (RWM). RWM is
popularly known as Random Access Memory (RAM) :‐
ROM (read-only memory)
>>programmed permanently at the factory, cannot be altered
EPROM (erasable programmable ROM)
>>nonvolatile, written electrically but erased optically
EEPROM (electrically ROM)
>>nonvolatile, both written and erased electrically RAM (random-access memory)
( RWM read and write memory
ROM (read-only memory)
-
8/20/2019 Microprocessor Notes 1
13/15
>>The registers inside the microprocessor –Read OnlyMemory (ROM)
>>used to store information that does not change. –It is used to store programs and data that need not to be altered,
i.e. permanent storage. Programs and data stored in ROMs can
only be read by the CPU.
>>Special equipment is used to write programs and data into the
ROMs and is called EPROM Programmer.
>>The monitor program is normally stored in the ROM.
>>Monitor program is actually the ‘resource manager’ of the
microcomputer system, similar to DOS or Windows in a personal
computer.
>>An example of a EPROM chip is the 2764 (8K X 8).
Random Access Memory (RAM)
(also known as Read/Write Memory(RWM)).>>used to store information supplied by the user. such as
programs and data.It is used to store user programs and data, and can be altered at
any time, i.e. temporary storage.
>>The information stored in RAM or RWM can be easily read and
altered by the CPU.
>>The contents (data or programs) stored is lost if power supply
to this chip is turned off. An example of a RWM chip is the CMOS
6116 (2K
X
8).
-
8/20/2019 Microprocessor Notes 1
14/15
Memory Map and AddressesThe memory map is a picture representation of the
address range and shows where the different memorychips are located within the address range.
To execute a program:>>the user enters its instructions in binary
format into the memory.
>>The microprocessor then reads these
instructions and whatever data is needed from
memory, executes the instructions and places the
-
8/20/2019 Microprocessor Notes 1
15/15
results either in memory or produces it on an
output device.
The three cycle instruction executionmodel
Fetch, Decode and Execute Cycles >>To use the right names for the cycles:–The
microprocessor fetches each instruction,– decodesit,–
Then executes it.>>To execute a program, the microprocessor
“reads” each instruction from memory, “interprets”
it, then “executes” it.
>>This sequence is continued until all instructions
are performed.