Introduction to 8051 Microcontroller

8/13/2019 Introduction to 8051 Microcontroller

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1. Introduction1. Definition of microcontroller 2. 8051 microcontroller

1. Basics. 2. I/O Ports. 3. Interrupts (Timer, Serial, External Interrupts).

2. How to program 8051. 1. In assembly.

2. In C 3. Basic programming (delay and other pins basic I/O functions).


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4. Timer/counter. 1. Basic timer operations2. Timer interrupts. 3. Counter programming.

4. Some basic codes. 5. LCD and Keypad interfacing. 6. Serial Port Programming

1. Basic serial communication.

2. Serial communication modes. 3. Serial communication registers. 4. Basic serial communication programming in C.

7. Other Interrupts Programming. 1. External interrupt programming.


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Definition of microcontroller.

CPU

GeneralPurposeMicro-

processor

RAM ROM I/O Ports Timers Serial COMPort

General Purpose Microprocessor System


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The 8051 Microcontroller

Feature 8051 8052 8031

ROM (on-chip program

space in bytes)

4K 8K 0K

RAM (Bytes) 128 256 128

Timers 2 3 2

I/O Pins 32 32 32

Serial Port 1 1 1

Interrupt Sources 6 8 6

Comparison with other Intel microcontrollers


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Part Number ROM RAM I/O Pins Timer Interrupt Vcc Packaging

AT89C51 4K 128 32 2 6 5V 40

AT89LV51 4K 128 32 2 6 3V 40

AT89C1051 1K 64 15 1 3 3V 20

AT89C2051 2K 128 15 2 6 3V 20

AT89C52 8K 128 32 3 8 5V 40

AT89LV52 8K 128 32 3 8 3V 40

Note: C Indicates the CMOS


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Port 0Port 1Port 2Port 3


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Interrupt Vector Table for 8051

Interrupt ROM location (HEX) Flag Clearing

Reset 0000 Auto

External hardware interrupt 0 (INT0) 0003 Auto

Timer 0 interrupt 000B Auto

External hardware interrupt 1 (INT1) 0013 Auto

Timer 1 interrupt 001B Auto

Serial COM interrupt (RI and TI) 0023 Programmer clears it.


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D7 D0

EA ---- ET2 ES ET1 EX1 ET0 EX0

EA IE7 Disable all interrupts. If EA=0, no interruptis acknowledged. If EA=1 each interruptsource is individually enabled or disabledby setting or clearing its enable bit.

---- IE6 Not ImplementedET2 IE5 Enable or disable Timer 2 overflow or

capture interrupt (8052 only).

ES IE4 Enables or disable serial port interrupt

ET1 IE3 Enables or disable Timer 1 overflowinterrupt

EX1 IE2 Enable or disable external interrupt 1

ET0 IE1 Enables or disable Timer 0 overflowinterrupt

EX0 IE0 Enable or disable external interrupt 0

IE (Interrupt Enabler) Register


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MOV Instructionmov destination,source;

ADD Instructionadd A,sourc; add source operand to the accumulatorand store the result in A.

JUMP Instruction

Conditional Jumps.JZ(Jump if Zero if A=0)DJNZ(Decrement and jump if not zero)JNC( Jump if not Carry set CY=0)JC(Jump if carry set CY=1)


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Unconditional JumpsLJMP(Long Jump)

It is a 3byte instruction 1 st byte is used for opcodethe remaining 2 bytes are used for address.

SJMP(Short Jump)It is a 2 byte instruction 1 st byte is used for opcodethe remaining 1 byte is used for address.

CALL InstructionsLCALL(Long Call)

It is also a 3 byte instruction.ACALL(Absolute Call)

It is a Two byte instruction used to call a functionoutside the function being executed.


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Role of Stack Pointer for Call Instruction

PUSH and POP Instructions

NOP(No operation) Instruction


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Include header file#include

The Main FunctionVoid main(void){}

Decision Making Instructionswhile loop

while(condition) //the program remains in the loop whilethe condition is truefor loopfor(initialization;condition;increment/decrement)


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The if else statementsif(condition 1){}else if(condition 2){}else{}


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Some Basic C programs


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Timer 0 and Timer 1D15 D14 D13 D12 D11 D10 D9 D8 D7 D6 D5 D4 D3 D2 D1 D0

D0-D7 are known as TLxD8-D15 are known as THx


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The TMOD (Timer Mode) Register(MSB) (LSB)GATE C/T M1 M0 GATE C/T M1 M0

Timer 1 Timer 0

GATE gating control when set. The timer/counter is enabled onlywhen the INTx pin is high and the TRx pin is set.When cleared, the timer is enabled whenever the TRx control bit isset.C/T Timer or Counter selected cleared for timer operation (inputfrom internal system clock). Set for counter operation (input fromTx input pin).M1 Mode bit 1

M0 Mode bit 0


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M1 M0 Mode Operation Mode0 0 0 13-bit timer mode 8-bit

timer/counter THx with TLxas 5 bit presaler

0 1 1 16-bit timer mode 16-bittimer/counter THx and TLxare cascaded; there is noprescaler

1 0 2 8-bit auto reload 8 bit autoreload timer/counter;THxholds the value that is to bereloaded into TLx each timeit overflows.

1 1 3 Split timer mode

The TMOD (Timer Mode) Register.


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The TCON (Timer Control) RegisterD7 D0TF1 TR1 TF0 TR0 IE1 IT1 IE0 IT0

TF1 TCON7 Timer 1 overflow flag. Set by hardware when timer/counter 1 overflows. Cleared by hardware as the processor vectors tothe interrupt service routine.

TR1 TCON6 Timer 1 run control bit. Set/cleared by the software to turn timer/counter 1 on/off.

TF0 TCON5 Timer 0 overflow flag. Set by hardware when timer/counter 0 overflows. Cleared by hardware as the processor vectors to theinterrupt service routine.

TR0 TCON4 Timer 0 run control bit. Set/cleared by the software to turn timer/counter 0 on/off.

IE1 TCON3 External interrupt 1 edge flag. Set by CPU when the external interrupt edge (H-to-L transition) is detected.

IT1 TCON2 Interrupt 1 type control bit. Set/cleared by software specify falling edge/low level triggered external interrupt

IE0 TCON1 External interrupt 0 edge flag. Set by CPU when the external interrupt edge (H-to-L transition) is detected.

IT0 TCON0 Interrupt 0 type control bit. Set/cleared by software specify falling edge/low level triggered external interrupt


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Timers and Counters Programs


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Simplex Serial communication

System 1

Transmitter

System 2

Receiver


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Half Duplex Serial Communication

System 1

Transmitter

System 2

Receiver

Receiver Transmitter


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System 1

Transmitter

System 2

Receiver

Receiver Transmitter

Full Duplex Serial Communication


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The SCON (Serial Control) RegisterSCON 7 SCON 6 SCON 5 SCON 4 SCON 3 SCON 2 SCON 1 SCON 0

SM0 SM1 SM2 REN TB8 RB8 TI RI

SM0 SCON7 Serial port mode specifier

SM1 SCON6 Serial port mode specifier

SM2 SCON5 Used for multiprocessor communication. (Make it 0.)

REN SCON4 Set/cleared by software to enable/disable reception.

TB8 SCON3 Not widely used (Make it 0)

RB8 SCON2 Not widely used (Make it 0)

TI SCON1 Transmit interrupt flag. Set by the hardware at the beginning of the stop bit in mode 1, must becleared by software.

RI SCON0 Receive interrupt flag. Set by the hardware halfway through the stop bit time in mode 1. Must becleared by software.


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SM0 SM10 0 Serial mode 0

0 1 Serial Mode 1, 8-bitdata, 1 stop bit, 1start bit

1 0 Serial Mode 2

1 1 Serial Mode 3

The SCON (Serial Control) Register

Serial Communication Modes of 8051


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Serial Communication Codes


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External Interrupt Programming


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Documents

Introduction to 8051 Microcontroller