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18/03/2016
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MECHATRONICS SYSTEM DESIGN
(MtE-325)
TODAYS LECTURE
Introduction to Microprocessor System Hardware
Introduction to Microprocessor Operation
Interface to a Microprocessor Controller
The Parallel Interface
Digital to Analog Conversion
Analog to Digital Conversion
The Serial Interface
RS-232
Introduction to Controller Programming
Microprocessor-based Controllers
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INTRODUCTION TO
MICROPROCESSOR SYSTEM
HARDWARE
MICROPROCESSOR VS MICROCONTROLLER
• A microprocessor by itself is not a computer; additional
components such as memory and input/output circuits are
required to make it operational.
• However, the microcontroller does contain all the
computer functions on a single IC.
• Microcontrollers lack some of the power and speed of the
newer microprocessors, but their compactness is ideal for
many control applications.
• Majority of the so-called microprocessor-controlled devices,
such as vending machines, are really using
microcontrollers.
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MICROPROCESSOR SYSTEM HARDWARE
MICROPROCESSOR SYSTEM HARDWARE
A computer is made up of four basic functional units:
1. Central processing unit (CPU)
2. Memory
3. Inputs
4. Outputs
The central processing unit does the actual computing
and is composed of two subparts: the arithmetic logic unit (ALU) and
control sections
The arithmetic logic unit performs the actual numerical and logic
calculations such as addition, subtraction, AND, OR, and so on.
The control section of the CPU manages the data flow, such as reading
and executing the program instructions.
If data require calculations, the control section hands it over to the ALU
for processing.
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MICROPROCESSOR SYSTEM HARDWARE
Binary to decimal conversion Decimal to binary conversion
MICROPROCESSOR SYSTEM
HARDWARE…MEMORYComputers usually have two kinds of addressable memory. The first is
random-access memory (RAM). Also called read/write memory, or RWM.
All data in this type of memory are lost when the power is turned off and is
called volatile memory.
The second type of memory is read-only memory (ROM), which is similar to
RAM except that new data cannot be written in.
This type of memory does not lose its data when power is turned off and is
called non-volatile memory.
Most microprocessor systems have both RAM and ROM. RAM is used for
temporary program storage and as a temporary scratch-pad memory for the
CPU. Whereas ROM is used to store programs and data that need to be
always available.
Actually, many computers use an EPROM (erasable programmable read-only
memory) or an EEPROM (electrically erasable programmable ROM) instead
of a ROM for long-term memory.
EPROMs can be erased with a strong UV light and reprogrammed.
EEPROMs can be erased and reprogrammed electrically.
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MICROPROCESSOR SYSTEM
HARDWARE…I/O SECTION
• The input/output (I/O) section of the computer allows it to interface with
the outside world.
• The input section is the conduit through which new programs and data
are
• entered into the computer,
• whereas the output section allows the computer to communicate its
results.
• An I/O interface is called a port.
• An input port is a circuit that connects input devices to the computer;
examples of input devices are keyboards, sensors, and switches.
• An output port is a circuit that connects the computer to output devices.
• Examples of output devices are indicator lamps, actuators, and
monitors.
MICROPROCESSOR SYSTEM HARDWARE
• The address bus is a group of wires that carries an address (in binary
form) from the CPU to the memory and I/O circuits.
• The data bus is a group of wires that carries the actual numerical data
from place to place within the computer.
• Data flow in both directions on the data bus. For example, input data
enter through the input port and proceed through the data bus to the
CPU.
• If the CPU needs to store this data, it will send it back through the data
bus to memory.
• The control bus consists of timing and event-control signals from the
CPU. These signals are used to control the data flow on the data bus.
• For example, one of the control signals is the read/write (R/W) line. This
signal informs the memory if the CPU wishes to read existing data out of
memory or write new data into memory.
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INTRODUCTION TO
MICROPROCESSOR OPERATION
MICROPROCESSOR SYSTEM OPERATION
Each type of microprocessor has its own instruction set, which is the
set of commands that it was designed to recognize and obey.
Microprocessor instructions are very elemental and specific.
Many microprocessor instructions simply move data from one place to
another within the computer; others perform mathematical or logic
operations. Still another group of instructions control program flow,
such as jumping forward or backward in the program.
Each instruction in the instruction set is assigned its own unique
operation code, (which is typically 8 bits long and referred to as the op-
code). The CPU uses this 8-bit number to identify the instruction.
A machine language program is a list of instructions (in op-code form)
for the microprocessor to follow. Before the program can be executed, it
must first be loaded sequentially into memory. The op-code for the first
instruction is loaded at the first address location, the op-code for the
second instruction is loaded next in line, and so on.
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MICROPROCESSOR SYSTEM OPERATION
MICROPROCESSOR SYSTEM OPERATION
The program shown on the next slide directs the CPU to get 1 byte of
data from input port 01, add 1 to it, and send the result to output port
02.
Before execution can start, the address of the first instruction must be
loaded into the program counter.
The program counter is a special address-storage register that the
CPU uses to keep track of where it is in the program, much like a
bookmark.
The program counter always holds the address of the next instruction
to be executed.
Once the microprocessor is activated, execution of the program is
completely automatic. The execution process is a series of fetch-execute
cycles, whereby the microprocessor first fetches the instruction from
memory and then executes it.
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INTERFACING TO A
MICROPROCESSOR CONTROLLER
Parallel Port
Digital to analog conversion
Analog to digital conversion
Serial port
INTERFACING
An important part of any control system is the link between the controller
and the real world. For a digital controller, data enter and exit through a
parallel interface or through a serial interface.
The parallel interface transfers data 8 bits (or more) at the same time,
using eight separate wires.
It is essentially an extension of the data bus into the outside world.
The parallel interface is ideal for inputting or outputting data from
devices that are either on or off.
For example, a single limit switch uses only one input bit, and an on-off
signal to a motor requires only one output bit.
These 1-bit signals are called logic variables, and eight such signals can be
provided from a single (8-bit) port.
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INTERFACING…..DIGITAL TO ANALOG
CONVERTER (DAC)
• The digital-to-analog converter (DAC) is a circuit that converts a digital
word into an analog voltage.
• Figure on the next slide shows the block diagram of a typical 8-bit DAC.
• The input is an 8-bit digital word.
• The output is a current that is proportional to the binary input value
and must be converted to a voltage with an op-amp.
• A stable reference voltage (Vref) must be supplied to the DAC.
• This voltage defines the maximum analog voltage—that is, for a digital
input of 11111111, Vout is essentially Vref.
• If the input is 00000000, the Vout will be 0 Vdc.
• For all values in between, the output voltage is a linear percentage of
Vref.
INTERFACING…..DIGITAL TO ANALOG
CONVERTER (DAC)
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INTERFACING…..DIGITAL TO ANALOG
CONVERTER (DAC)
• Specifically, the output voltage for any digital input (for the 8-bit DAC)
is
INTERFACING…..ANALOG TO DIGITAL CONVERTER
(ADC)
An analog-to-digital converter (ADC) is a circuit that converts an
analog voltage into a digital word.
The output voltage for any analog input (for the 8-bit ADC) is
EXAMPLE 2.3
EXAMPLE 2.4
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Analog-to-digital converter (ADC) block diagram.
INTERFACING…..ANALOG TO DIGITAL CONVERTER
(ADC)
THE SERIAL INTERFACE
In a serial interface, the data are sent 1 bit after the other on a
single wire.
Because data always exist in a parallel form inside the computer,
it must be converted to serial data before coming out the serial
port.
This is accomplished with a special parallel-to-serial converter IC
called a universal asynchronous receiver transmitter
(UART).
On the other end of the line, a receiver must convert the serial
data back into parallel data, which is done with another UART.
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Components in a serial interface circuit.
THE SERIAL INTERFACE (CONT’D)
Serial data are classified as;
1. Synchronous
Synchronous data require that the data bytes be sent as a group
in a “package.” It is used in sophisticated communication systems
that move a lot of data
2. Asynchronous
synchronous data transfer is the more common (but slower) type
of serial transfer and allows for individual bytes to be sent when
needed.
The other important parameter in serial transmission is the
number of bits sent per second (frequently called the baud rate.
Standard bit rates are 300 bps (bits per second), 1200 bps, 2400
bps, 9600 bps, 14,400 bps 28,800 bps, 33,600 bps, and 57,600 bps.
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Serial data format for the binary word 10110010.
THE SERIAL INTERFACE (CONT’D)
RS 232
In order to make the serial interface practical, a set of
specifications called the RS-232 standard was established.
Officially, the RS-232 standard specifies the serial data
interface between data terminal equipment (DTE) and data
communication equipment (DCE).
A common application of RS-232 is the interface between a
PC and the modem, in which case the computer is the DTE
and the modem is the DCE
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THE SERIAL INTERFACE (CONT’D)
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The RS-232 serial interface.
Networking
Probably the most common use of serial data is innetworking.
Network cabling differs depending on the type of localarea network (LAN).
Typically, each unit on the network has a unique address number and also address detection circuitry.
When one unit wants to talk to another unit, it first broadcasts the address of the unit its wants to talk to (serially, of course, on the signal wire) and then sends the data (serially), which consists of some number of bytes.
THE SERIAL INTERFACE (CONT’D)
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Concept of local area network (LAN) interconnections for bus topology.
INTRODUCTION TO
CONTROLLER
PROGRAMMING
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A digital controller is a computer operating in real time.
The program is running all the time—repeatedly taking in
the newest sensor data and then calculating a new output
for the actuator.
The basic structure of a controller program is a loop.
In a loop structure, the same sequence of instructions is
executed over and over again, and each pass through the
loop is called an iteration, or scan.
INTRODUCTION TO CONTROLLER
PROGRAMMING
A generalized controller program.
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MICROPROCESSOR-BASED
CONTROLLERS
MICROPROCESSOR-BASED CONTROLLERS
Single-Chip Microcomputers (Microcontrollers)
The Motorola 68HC11
Intel 8051 microcontroller
PIC 16C72 microcontroller
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Motorola 68HC11 microcontroller block diagram
Intel 8051 microcontroller block diagram
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PIC 16C72 micro controller block diagram
Single-Board Computers are off-the-shelf microprocessor-
based computers built on a single printed-circuit card.
Programmable Logic Controllers (PLC’s) is a self-
contained microprocessor-based unit, designed specifically to
be a controller.
The PLC includes an I/O section that can interface directly
to such system components as switches, relays, small
motors, and lights.
MICROPROCESSOR-BASED CONTROLLERS
(CONT’D)
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Personal Computers Used in Control Systems The
availability of relatively low-cost, off-the-shelf personal
computers (PCs) has made them an attractive alternative for
small, one-of-kind control applications.
Control system software packages are commercially
available for the PC that run under DOS and Windows.
A standard PC comes with expansion slots, which are
circuit-card connectors emanating from the motherboard
(main board) of the computer.
MICROPROCESSOR-BASED CONTROLLERS
(CONT’D)
