Microcontroller Workshop

MICROCONTROLLER AND ITS APPLICATION WORKSHOP January 26, 2007 Usman Institute of Technology, Karachi. Noman Ahmed Lecturer SSUET E-mail: [email protected]

Introduction 

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It is hard to imagine the present world of electronic devices without the microprocessor.  Cash register, scales, ovens, washing machine, alarm clock, thermostats, and ignition system, etc. 1971 (Microprocessors)  Intel 8080, Motorola 6800, RCA 1801, MOS Technology and Zilog Z80. 1976 (Microcontrollers)  Intel 8748 (MCS-48 family)  17,000 transistors • CPU, 1KB EPROM, 64B RAM, 27 I/O pins, and an 8-bit timer. • Used in washing machines and traffic light controllers. 1980 (Microcontrollers)  Intel 8051 (MCS-51 family)  60,000 transistors • CPU, 4KB ROM, 128B RAM, 32 I/O Pins, a serial port, two 16-bit timers.

A Computer System 

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

Computer is defined by two key traits:  The ability to be programmed to operate on data without human intervention.  The ability to store and retrieve data. More generally, a computer system includes  Peripheral devices for communicating with the human. (hardware)  Program that process data. (software) A Computer system contains  Central process unit (CPU) connected to random access memory (RAM) and read-only memory (ROM) via the address bus, data bus, and control bus. Interface circuits connect the system buses to peripheral devices. (see next slide)

Block Diagram of Computer System

What’s a Microcontroller? 

A Microcontroller is a computer-on-a-chip, or, if you prefer, a single-chip computer. Micro suggests that the device is small, and controller tells you that the device might be used to control objects, processes, or events.

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Another term to describe a microcontroller is embedded controller, because the microcontroller and its support circuits are often built into, or embedded in, the devices they control.

Where it Required 

Any device that measures, stores, controls, calculates, or displays information is a candidate for putting a microcontroller inside.

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Application  Automobiles  Security System  Answering Machine  Cellular Phone  Microwave  Keyless entry  Fax machine  Toys  Camera

Microprocessors vs. Microcontroller Hardware Achitecture  Whereas a microprocessor is a single-chip CPU, a microcontroller contains a CPU and much of the remaining circuitry of a complete microcomputer system in a single IC.  Microcontrollers (as control oriented devices) are called upon to response to external stimuli in real time.  They must perform fast context switching, suspending, one process while executing another in response to an ‘event’ (opening the oven’s door).  Applications  Microcontrollers are suitable to ‘control’ of I/O devices in designs requiring a minimum component count, whereas microprocessors are suitable to ‘processing’ information in computer systems. 

Microprocessors vs. Microcontroller 

(cont.) Instruction set features 

Microprocessor instruction sets are ‘processing intensive’ implying they have powerful addressing modes with instructions catering to operations on large volumes of data. Microcontrollers, on the other hand, have instruction sets catering to the control of inputs and outputs.



Microcontrollers have built-in circuitry and instructions for input/output operations, event timing, and enabling and setting priority levels for interrupts caused by external stimuli. Microprocessors often require additional circuitry (serial interface Ics, interrupt controllers, timers, etc. ) to perform similar operations.

Hardware Architecture 

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The MCS-51 is a family of microcontroller ICs developed, manufactured, and marketed by Intel. Other IC manufacturers are  Siemens, Advanced Micro Devices (AMD), Fujitsu, Philips are licensed ‘second source’ suppliers of devices in the MCS-51 family. The generic MCS-51 IC is the 8051, the first device in the family offered commercially. Its features are summarized  4KB ROM (64KB external code memory space)  128B RAM (64KB external data memory space)  8-bit I/O ports (4EA)  16-bit timers (2EA)  Serial interface  Boolean processor  210 bit-addressable locations

Comparison of MCS-51 ICs Part No. 8051

ROM/EPROM 4K ROM

8031

RAM

Timers

128B

2

128B

2

8751

4K EPROM

128B

2

8052

8K ROM

256B

3

256B

3

256B

3

8032 8752

8K EPROM

8051 Block Diagram INT1 INT2

Note: bold-faced pin assignments for P1 and P3.

Timer 1 Timer 0 Serial port Interrupt Control

Other registers

128B RAM

4KB ROM

Timer 1

T1

Timer 0

T0

CPU

Bus Control

I/O ports

Serial port

Oscillator

EA

RST

PSEN

ALE

P0 P1 P2 P3 Address/data

TXD

RXD

8051 Pinouts 30pF XTL1 (19)

VCC (40)

XTL2 (18)

30pF (29) (30) (31) (9)

Port 3

RD(17) WR(16) T1(15) T0(14) INT1(13) INT0(12) TXD(11) RXD(10)

PSEN ALE EA RST

P3.7 P3.6 P3.5 P3.4 P3.3 P3.2 P3.1 P3.0

8051

VSS(20)

P0.7 P0.6 P0.5 P0.4 P0.3 P0.2 P0.1 P0.0 P1.7 P1.6 P1.5 P1.4 P1.3 P1.2 P1.1 P1.0

AD7(32) AD6(33) AD5(34) AD4(35) AD3(36) AD2(37) AD1(38) AD0(39) (8) (7) (6) (5) (4) (3) (2) (1)

P2.7 P2.6 P2.5 P2.4 P2.3 P2.2 P2.1 P2.0

A15(28) A14(27) A13(26) A12(25) A11(24) A10(23) A9(22) A8(21)

Port 0

Port 1

Port 2

I/O Ports 

32 of the 8051’s 40 pins function as I/O port lines. However, 24 of these 32 lines are dual-purpose. 





Dual purpose: can operate as I/O, control line, or part of address/data bus. The 8-line in a port can be treated as a unit in interfacing to parallel devices such as printers, A/D converters, and so on. Or, each line can operate independently in interfacing to single-bit devices such as switches, LEDs, transistors, motors, and loudspeakers.

I/O Ports 

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Port 0  Is a dual-purpose port on pins 32-39 of the 8051 IC.  In minimum-component designs, • It is used as a general purpose I/O port.  For larger designs with external memory, • It becomes a multiplexed address and data bus. Port 1  Is a dedicated I/O port on pins 1-8.  The pins are available for interfacing to external devices as required. Port 2  Is a dual-purpose port on pins 21-28 of the 8051 IC.  As a general purpose I/O port  Or as the high-byte of the address bus for designs with external ROM or more than 256B of RAM.

I/O Ports (cont.) 

Port 3  Is a dual-purpose port on pins 10-17 of the 8051 IC.  As a general purpose I/O port  These pins are multifunctional, with each having an alternate purpose related to special features of the 8051.

BIT NAME

BIT

functions

P3.0 RXD

B0H

Receive data for serial port

P3.1 TXD

B1H

Transmit data for serial port

P3.2 INT0

B2H

External interrupt 0

P3.3 INT1

B3H

External interrupt 1

P3.4 T0

B4H

Timer/counter 0 external input

P3.5 T1

B5H

Timer/counter 1 external input

P3.6 WR

B6H

External data memory write strobe

P3.7 RD

B7H

External data memory read strobe

Control Signals 

PSEN (Program Store Enable) 

Is an output signal on pin 29.



It is a control signal that enables external program (code) memory (ROM).

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



It usually connects to an EPROM’s output enable (OE) pin to permit reading of program bytes. The PSEN signal pulses low (active stage) during the fetch stage of an instruction, which is stored in external program memory. The binary codes of a program (opcode) are read from EPROM, travel across the data bus, and are latched into the 8051’s instruction register (IR) for decoding.

Control Signals 

ALE (Address Latch Enable) 

Is an output signal on pin 30.



It is used for de-multiplexing the address and data bus.





When port 0 is used in its alternate mode – as the data bus and low-byte of the address bus – ALE is the signal that latches the address into an external register during the first-half of a memory cycle. This done, the port 0 lines are then available for data input or output during the second-half of the memory cycle. The ALE signal pulses at 1/6th the on-chip oscillator frequency

Control Signals 

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EA (External Access)  Is an input signal on pin 31.  Is generally tied high (5V) or low (ground).  If high • The 8051 executes programs from internal ROM when executing in the lower 4K/8K of memory.  If low • Programs execute from external memory only (and PSEN pulses low) RST (Reset)  Is an input signal on pin 9.  When this signal is brought high for at least 2 machine cycles, the 8051 internal registers are loaded with appropriate values for an orderly system start-up.  For normal operation, RST is low.

Memory Organization 

Most microprocessors implement a shared memory apace for data and programs. Both the data and programs reside in the system RAM. Microcontroller, on the other hand, the control program must reside in ROM.

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The internal memories consist of ROM and RAM. The RAM contains a rich arrangement of general-purpose storage, bit addressable storage, register banks, and special function registers.

RAM 7F

General-purpose RAM (80 bytes)

FF

30 2F

Special Function Registers (SFR)

Bit-addressable locations (16 bytes)

20 1F

Bank registers (32 bytes)

00

80

General-Purpose RAM 7F

General-purpose RAM (80 bytes)

30 2F

Ex: To read the contents of internal RAM address 5FH into the accumulator. Solution1:(direct address mode)

MOV A, 5FH Solution2:(immediate addressing & indirect address mode) 20 1F

Bank registers (32 bytes)

00

MOV R0, #5FH MOV A, @R0

210 (128+82) Bit-Addressable RAM 7F

FF

30 2F

Special Function Registers (SFR)

Bit-addressable locations (16 bytes)

(82 bits)

(128 bits)

20 1F

00

80

The idea of individually accessing bits through software is a powerful feature of most microcontroller.

128 General-Purpose Bit-Addressable Locations 2F

7F

7E

7D

7C

7B

7A

79

78

2E

77

76

75

74

73

72

71

70

2D

6F

6E

6D

6C

6B

6A

69

68

2C

67

66

65

64

63

62

61

60

2B

5F

5E

5D

5C

5B

5A

59

58

2A

57

56

55

54

53

52

51

50

29

4F

4E

4D

4C

4B

4A

49

48

28

47

46

45

44

43

42

41

40

27

3F

3E

3D

3C

3B

3A

39

38

26

37

36

35

34

33

32

31

30

25

2F

2E

2D

2C

2B

2A

29

28

24

27

26

25

24

23

22

21

20

23

1F

1E

1D

1C

1B

1A

19

18

22

17

16

15

14

13

12

11

10

21

0F

0E

0D

0C

0B

0A

09

08

20

07

06

05

04

03

02

01

00

Register Banks 1F 18

R7 ~R0

17 10

R7 ~R0

Bank 2 (8 bytes)

0F 08

R7 ~R0

Bank 1 (8 bytes)

07 00

R7 ~R0

Bank 3 (8 bytes)

Bank 0 (8 bytes)

Ex: Read the contents of address 05H into the accumulator. Solution: (Register address mode) MOV A, R5 (only 1-byte) Solution: (direct address mode) MOV A, 05H (2-byte instruction)

21 Special Function Registers (SFR) F0 E0 D0 B8 B0 A8 A0 99 98 90 8D 8C 8B 8A 89 88 87 83 82 81 80

F7 E7 D7 B7 AF A7

F6 E6 D6 B6 A6

F5 E5 D5 B5 A5

9F 97

9E 96

9D 95

8F

8E

8D

87

86

85

F4 F3 E4 E3 D4 D3 BC BB B4 B3 AC AB A4 A3 Not bit addressable 9C 9B 94 93 Not bit addressable Not bit addressable Not bit addressable Not bit addressable Not bit addressable 8C 8B Not bit addressable Not bit addressable Not bit addressable Not bit addressable 84 83

F2 E2 D2 BA B2 AA A2

F1 E1 B9 B1 A9 A1

F0 E0 D0 B8 B0 A8 A0

9A 92

99 91

98 90

8A

89

88

82

81

80

B ACC PSW IP P3 IE P2 SBUF SCON P1 TH1 TH0 TL1 TL0 TMOD TCON PCON DPH DPL SP P0

Addressing Modes 

The 8051 is capable of performing direct and indirect memory accesses on its various memory spaces.

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These are the typical methods through which processor systems access memory.

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Addressing modes are in integral part of each computer’s instruction set. There are 8 modes available: 

Register, Direct, Indirect, Immediate, Relative, Absolute, Long, and Indexed.

Instruction Set 

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The MCS-51 instruction set is optimized for 8-bit control applications.  It provides a variety of fast, compact address modes for accessing the internal RAM to facilitate operations on small data structures. The 8051 instructions have 8-bit opcodes  28 = 256 instructions.  255 are implemented and 1 is undefined.  There are 139 one-byte instructions, 92 two-byte instructions, and 24 three-byte instructions. (139+92+24=255)

Instruction Set (cont.) 

Types of Instruction 

Arithmetic Instructions

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Logical Instructions

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Data Transfer Instructions

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Boolean Instructions

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Program Branching Instructions

INTERFACING OF DIFFERENT COMPONENTS WITH MICROCONTROLLER

Input Devices  On-Off switch  Push button  Limit Switch  IR sensor  Metal Detector  DTMP Decoder  KEY Pad

Output Devices  Leds  Relay  Solenoid  Seven segment  LCD display  Dot Matrix display  Stepper Motor

Interfacing of LCD 8051

LCD P1.0 ~ P1.7

D0 ~ D7 Rs

P2.0 P2.1 P2.2

VCC 10K VEE R/W

E VSS

Temperature Sensor Physical data (temperature, light, flow, speed, and etc.)

Transducers (Sensors)

o

Thermistor Temperature

Output Electrical Signals (current, voltage, resistance, capacitance, and etc.)

Resistance

C

K Ohm

0

29.49

25

10

50

3.893

75

1.7

100

0.817

Interfacing of ADC808/809  

ADC808/809 Chip with 8 analog channel. This means this kind of chip allows to monitor 8 different transducers. ADC804 has only ONE analog input: Vin(+). ADC808

8 channels (IN0~IN7)

D0 ~ D7 GND

channel

CBA

CLK

EOC

IN0

000

VCC Vref(+)

OE

IN1

001

IN2

010

IN3

011

IN4

100

IN5

101

IN6

110

IN7

111

Vref(-) SC ALE

C BA

Interfacing of Stepper Motor  

Stepper motor translates electrical pulses into mechanical movement (for position control). Applications: Disk Driver, Dot matrix printer, robotics.

A N S

C N

4 Step Sequences S N

S

B

D

Step A s

B

C

D

1 2 3 4

0 1 1 0

0 0 1 1

1 0 0 1

1 1 0 0

Interfacing of Keyboard Keyboard and LCDs are the most widely used input/output devices of the 8051, and a basic understanding of them is essential.  See Figure 

Project Steps Putting together a microcontroller project involves several steps: 1. Define the task 2. Design and build the circuits 3. Write the control program 4. Test and debug 

Sometimes the steps won’t follow exactly in this order.

Projects  Digital Clock  Keyless entry  Mobile Automation  Robotic Arm  Elevator Control System  Industrial Network  DC/AC Drive

Projects  PABX  Autonomous Robot  Infant incubator  Attendace System  Car Tracking  Score Board  Prepaid Energy meter  CNC PCB drill machine