UNIT-I MICRO CONTROLLER & INTERFACING NOTES

 VI semester                                                                                          paper -VII

 Title: Micro controllers and interfacing

Unit-1  :      Introduction to Microcontroller:

What is a Microcontroller?

          A microcontroller is a small, low-cost and self contained computer-on-a-chip that can be used as an embedded system.   (Or)   A microcontroller is a self-contained system with peripherals, memory and a processor that can be used as an embedded system.             

          Most programmable microcontrollers are used as embedded in other consumer products or machinery and household appliances for computer systems. Due to that, another name for a microcontroller is "embedded controller."

The basic structure of a microcontroller  :-

1.          CPU – CPU is brain of the Microcontroller. CPU used to fetch data, decode it and  complete the task successfully. With the help of CPU all the components of microcontroller is connected into a single system. Instruction fetched by the programmable memory is decoded by the CPU.

2.          Memory – In a microcontroller memory chip works same as microprocessor. Memory chip stores all programs & data. Microcontrollers are built with certain amount of ROM or RAM (EPROM, EEPROM, etc) or flash memory for the storage of program source codes.

3.          Input/output ports – I/O ports are basically employed to interface or drive different appliances such as- printers, LCD’s, LED’s, etc.

4.          Serial Ports – These ports give serial interfaces to microcontroller & various other peripherals such as parallel port.

5.          Timers – A microcontroller may be in-built with one or more timer or counters. The timers & counters control all counting & timing operations within a microcontroller. Timers are employed to count external pulses. The main operations performed by timers’ are- pulse generations, clock functions, frequency measuring, modulations, making oscillations, etc.

6.          ADC (Analog to digital converter) – ADC is employed to convert analog signals to digital ones. The input signals need to be analog for ADC. The digital signal production can be employed for different digital applications (such as- measurement gadgets).

7.          DAC (digital to analog converter) – this converter executes opposite functions that ADC perform. This device is generally employed to supervise analog appliances like- DC motors, etc.

8.          Interpret Control- This controller is employed for giving delayed control for a working program. The interpret can be internal or external.

9.          Special Functioning Block – Some special microcontrollers manufactured for special appliances like- space systems, robots, etc, comprise of this special function block. This special block has additional ports so as to carry out some special operations.

**Evolution of microcontrollers from 4 bit to 32 bit.

Intel first produced a microcontroller in 1976 is MCS-48, it is an 8 bit microcontroller. Later in 1980 they released a further improved version (which is also 8 bit), MCS-51. The most popular microcontroller 8051 belongs to the MCS-51 family of microcontrollers by Intel.

Global companies in semiconductor industry like Microchip, Zilog, Atmel, Philips, Siemens released products under their brand name.

A 4 bit microcontroller is used for a toys and clock frequencies. After that intel developed

·                  8 bit Microcontrollers

·                  16 bit Digital Signal Controllers (DSC)

·                  16 bit General Purpose Microcontrollers

·                  32 bit Micorcontrollers

       Intel developed  8051 is one of the most popular 8 bit micro controller it contains an instruction set with enough power and a large enough program space  by use with C Language.

 the 16 and 32 bit microprocessors has  sophisticated control capability & larger word widths and address spaces.  The development of microcontrollers has focused upon the integration of the facilities needed to support fast control into a single chip.

Intel has introduced standard 8-bit microcontroller 8048 in 1976. The same company has continued to drive the evolution of single chip microcontrollers.

 In the year 1980, Intel has introduced the 8051 microcontroller, with higher performance than 8048. With the advantages of 8051. The 8-bit microcontroller, 8051 family are the second generation world standard microcontrollers.

   In the advanced semiconductor technology, it is  possible to integrate more than 1.00.000 transistors on a single silicon chip. Intel has made use of this advanced process technology and developed a new generation of single chip 16 bit microcontrollers called the MCS-96 (8096 family).

The 8096 family offers the highest level of system integration on a single chip microcontroller with l,20,000 transistors. This 8096 microcontroller has 16 bit CPU, 8K bytes of program memory. 232 bytes of data memory and both analog and digital type of 1/ O features.

The Motorola Microcontroller family was first introduced  in 1978 and is built in the same pattern of the microprocessor 6800. The Microcontroller 6801 family was designed similar as the microprocessor 6800, its design and instruction set  modified to suit the control applications.

The microcontroller 6801 family includes On chip Input / Output ports, an Asynchronous serial communication device and 16 bit timer modules.

 The Microcontrollers 6801. 6803, 6805. 6811 are available from Motorola Company. The 6811 microcontroller family have different version with ROM, RAM, EPROM, and EEPROM.

 A micro controller is also known as embedded controller. Today various types of microcontrollers are available in market with different word lengths such as 4bit, 8bit, 64bit and 128bit microcontrollers.

 Difference between Microprocessor & Microcontrollers?

**Write a short note on Microcontroller  applications.

Microcontroller Applications:

     Microcontrollers usually low-power requirements for many devices. Microcontrollers are used in many consumer electronics, car engines, computer peripherals and test or measurement equipment. And these are well suited for long lasting battery applications

      Programmable microcontrollers are designed for embedded applications, unlike microprocessors  can be found in PCs. Microcontrollers are used in automatically controlled devices including power tools, toys, implantable medical devices, office machines, engine control systems, appliances, remote controls and other types of embedded systems.

 

Application of Microcontroller in Day to Day Life Devices:

·                  Light sensing & controlling devices

·                  Temperature sensing and controlling devices

·                  Fire detection & safety devices

·                  Industrial instrumentation devices

·                  Process control devices

Application of Microcontroller in Industrial Control Devices:

·                  Industrial instrumentation devices

·                  Process control devices

Application of Microcontroller in Metering & Measurement Devices:

·                  Volt Meter

·                  Measuring revolving objects

·                  Current meter

·                  Hand-held metering systems

**Explain the classification of microcontroller or types of microcontroller

      The microcontrollers are characterized as bus-width, instruction set, and memory structure. For the same family, there may be different forms with different sources. The types of microcontroller are characterized by their bits, memory architecture, memory/devices and instruction set.

Types of Microcontroller:

Microcontrollers are divided into categories according to their memory, architecture, bits and instruction sets.

Bits:

·                  8 bits microcontroller executes logic & arithmetic operations. Examples of 8 bits micro controller is Intel 8031/8051.

·                  16 bits microcontroller executes with greater accuracy and performance in contrast to 8-bit. Example of 16 bit microcontroller is Intel 8096.

·                  32 bits microcontroller is employed mainly in automatically controlled appliances such as office machines, implantable medical appliances, etc. It requires 32-bit instructions to carry out any logical or arithmetic function.

Memory:

External Memory Microcontroller – When an embedded system has a microcontroller unit  & that has not all the functional blocks available on a chip is called an external memory microcontroller. For example, 8031 has no program memory on the chip is an external memory microcontroller.

·  Embedded Memory Microcontroller –When an embedded system has a microcontroller unit that has all the functional blocks available on a chip is called an embedded microcontroller. For example, 8051 having program & data memory, I/O ports, serial communication, counters and timers and interrupts on the chip is an embedded microcontroller.

· CISC- CISC means complex instruction set computer, it allows the user to apply 1 instruction as an alternative to many simple instructions.

·  RISC- RISC means Reduced Instruction Set Computers. RISC reduces the operation time by shortening the clock cycle per instruction. this type of instruction sets reduces the design of microprocessor for industry standards. It allows each instruction to operate on any register or use any addressing mode and simultaneous access of program and data. The RISC gives a better execution than the CISC.

Memory Architecture:

Harvard Memory Architecture Microcontroller : The point when a microcontroller unit has a dissimilar memory address space for the program and data memory, the microcontroller has Harvard memory architecture in the processor.

 Program Memory of 8051

 Data Memory of 8051

Princeton Memory Architecture Microcontroller: The point when a microcontroller has a common memory address for the program memory and data memory, the microcontroller has Princeton memory architecture in the processor.

8051 Microcontroller:

The most universally employed set of microcontrollers come from the 8051 family.  The two other members of this 8051 family are-

·                  8052 – This microcontroller has 3 timers & 256 bytes of RAM. Additionally it has all the features of the traditional 8051 microcontroller. 8051 microcontroller is a subset of 8052 microcontroller.

·                  8031 – This microcontroller is ROM less, other than that it has all the features of a traditional 8051 microcontroller. For execution an external ROM of size 64K bytes can be added to its chip.

8051 microcontroller brings into play 2 different sorts of memory such as- NV-RAM, UV-EPROM and Flash.

** Explain the development tools for microcontroller .

Development tools for micro controllers:

The development system is used by system designers to design and test.

The microprocessor development system consists of a set of hardware and software tools.

The hardware of development system contains a standard pc, printer and an emulator. The software tools are also called program development tools.

They are editor, Assembler, Library builder, Linker, Debugger and simulator.

The software tools can be run on the PC to write, assemble, debug, modify and test the assembly language programs.

 The use of program development tools :

·                  Define the problem carefully.

·                  Use an editor to create the source file for ALP.

·                  Assemble the Source file with the assembler.

·                  If assembler list file indicates errors then use editor and correct the errors.

·                  Cycle through the edit-assemble loop until all errors indicated by assembler are cleared.

·                  Use linker to link all object files of program modes and library files  into a single executable file.

·                  If the linker indicates any error then modify the source program, re assemble and re link to correct the errors.

·                  If the developed program does not interact with any external hardware other than that directly connected to the system, then we can use the system debugger to run and debug our program.

·                  If the designed program is intended to work with external hardware  then use an emulator to run and debug the program.

·                   

** Write a short note on assembler.

Assembler:   The assembler is a software tool which ,when run on a PC ,converts the assembly language program to machine language program.

There are several types of assemblers, they are one pass assembler,two pass assembler, macro assembler, cross assembler, resident assembler and meta assembler.

One pass assembler is used to translate the source code, it is very fast but because of the forward reference problem, the one pass assembler is not used.

Most of the popularly used assemblers are two pass assembler. It is used to translate the source code into machine code.

The assembler usually generates two o/p files called  (1) object file and (2) List file.

Advantages of the assembler:

§  The  assembler translates mnemonics into binary code with speed and accuracy, thus eliminating human errors in looking up the codes.

§  The assembler assigns appropriate values to the variables used in a program. This feature offers flexibility in specifying jump locations.

§  It is easy to insert or delete instructions in a program and re assemble the entire program quickly with new memory locations and modified addresses for jump locations. This avoids rewriting the program manually.

§  The assembler checks syntax errors, such as wrong lables, opcodes, expressions etc.. and provides error messages. However it cannot check logic errors in a program.

§  The assembler can reserve memory locations for data or results.

§  The assembler provides list file for documentation.

**Write a short note on Simulator :

Simulator :   The simulator is a program which can be run on the development system to simulate the operations of the newly designed system. The operations can be simulated as

1.          Execute a program and display result.

2.          Single step execution of a program

3.          Break-point execution of a program

4.          Display the contents of register/memory.

 Simulator usually show the contents of registers and memory locations on the screen of computer and allow the system designer to perform all of the operations.

The simulators do not have the ability to perform actual I/O or internal hardware operations.

** Write a short note on Debugger.

Debugger:   The debugger is a software tool that allows the execution of a program in single step or break-point mode under the control of user. The process of locating and correcting the errors in a program using a debugger is known as debugging.

The debugger allows the designer to look at the contents of registers and memory locations after running the program.

It allows the system designer to change the contents of registers and memory locations and return the program.

Some debuggers allow the user to stop execution after each instruction, so that the memory/register content can be checked. A debugger also allows the user to set a break point at any point in user program.

When the user run the program the PC will execute instructions upto this break point and stop.

The user can then examine register and memory contents to see whether the results are correct upto that point.

 If the results are correct, the user can move the break point to a later point in the program. If the results are not correct, the user can check the program up to that point to find out why they are not correct.

The debugger tools help the user to isolate a problem in the program. Once the problem/errors are identified,

Tthe algorithm can be modified. Then the user can be use the editor  to correct the source program, re assemble the corrected source program, relink and run the program again.

** Write a short note on compiler.

Compiler:  Compiler is a program that transforms higher language source code(such as c code) to the lower language code(assembly language/machine code/binary code/object code).

                   This object code can be ported on any target such as microcontroller/processor. The reason for this conversion is to create an executable program for the desired target.

             

                 When the target compiled program runs on a computer/platform/system in which CPU/operating system is different from where compiler is installed,this compiler is referred as cross-compiler.

                    Tools such as µVision are widely used as compiler for different microcontroller variants. The µVision helps create and test embedded applications for ARM/Cortex-M C166/C251/C51 microcontrollers.

.                  A compiler creates machine code that runs on a processor with a specific Instruction Set Architecture (ISA).

                   Source-to-source compilers translate one program, or code, to another of a different language (e.g., from Java to C).

                   Choosing a compiler means first we need the ISA, operating system, and the programming language. When a CPU is completely useless without software to run on it. Compilers will report errors after compiling has finished.

 The Microcontrollers 6801. 6803, 6805. 6811 are available from Motorola Company. The 6811 microcontroller family have different version with ROM, RAM, EPROM, and EEPROM.

 A micro controller is also known as embedded controller. Today various types of microcontrollers are available in market with different word lengths such as 4bit, 8bit, 64bit and 128bit microcontrollers.