The 8051 microcontroller and embedded systems using assembly and c language

of Computer Science and Information Engineering National Cheng Kung University, TAIWAN Chung-Ping Young 楊中平 INTRODUCTION TO COMPUTING The 8051 Microcontroller and Embedded Systems: Usi

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www.elsolucionario.org

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The 8051 Microcontroller and Embedded

Systems Using Assembly and C

Second Edition

Muhammad Ali Mazidi Janice Gillispie Mazidi Rolin D McKinlay

8051 Hardware Connection and Hex File

8051 Timer/Counter Programming in Assembly and C

8051 Serial Port Programming in Assembly and C

Interrupts Programming in Assembly and C

8051 Interfacing to External Memory

8051 Real World Interfacing I: LCD,ADC AND SENSORS

LCD and Keyboard Interfacing

8051 Interfacing with 8255

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Home Automation, Networking, and Entertainment Lab

Dept of Computer Science and Information Engineering National Cheng Kung University, TAIWAN

Chung-Ping Young

楊中平

INTRODUCTION TO

COMPUTING

The 8051 Microcontroller and Embedded

Systems: Using Assembly and C

Mazidi, Mazidi and McKinlay

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OUTLINES Numbering and coding systems

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Department of Computer Science and Information Engineering

¾ There are only 0 and 1

¾ These two binary digits are commonly referred to as bits

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becomes zero

to obtain the binary number

Ex Convert 2510 to binary

Quotient Remainder 25/2 = 12 1 LSB (least significant bit)

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decimal number to a binary directly

Ex Convert 110012 to decimal

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¾ ex

It is much easier to represent a string of 0s and 1s such as

100010010110 as its hexadecimal equivalent of

C 1100

12

B 1011

11

A 1010

10

9 1001

9

8 1000

8

7 0111

7

6 0110

6

5 0101

5

4 0100

4

3 0011

3

2 0010

2

1 0001

1

0 0000

0

Hex Binary

Decimal

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equivalent hexadecimal number

¾ Start from the right and group 4 bits at a time, replacing each 4-bit binary number with its hex equivalent

¾ Each hex digit is replaced with its 4-bit binary equivalent

Ex Convert hex 29B to binary

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by repeated division, keeping track of the remainders

Ex Convert 4510 to hex

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by summing the weight of all digits

Ex 6B216 = 0110 1011 00102

1024 512 256 128 64 32 16 8 4 2 1

1 1 0 1 0 1 1 0 0 1 0

1024 + 512 + 128 + 32 + 16 + 2 = 171410

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least significant digits

¾ If the result is less than 16, write that digit

as the sum for that position

¾ If it is greater than 16, subtract 16 from it

to get the digit and carry 1 to the next digit

Ex Perform hex addition: 23D9 + 94BE

23D9 LSD: 9 + 14 = 23 23 – 16 = 7 w/ carry + 94BE 1 + 13 + 11 = 25 25 – 16 = 9 w/ carry

MSD: 2 + 9 = B

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first, borrow 16 from the preceding digit

Ex Perform hex subtraction: 59F – 2B8

59F LSD: 15 – 8 = 7 – 2B8 9 + 16 – 11 = 14 = E16

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NUMBERING

AND CODING

SYSTEMS

ASCII Code

assigns binary patterns for

represent each code

d 64

D 44

c 63

C 43

b 62

B 42

a 61

A 41

Symbol Hex

Selected ASCII codes

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HANEL

DIGITAL

PRIMER

Binary Logic

as the two digits 0 and 1

distinct voltage levels with built-in tolerances for variations in the voltage

either of the two shaded areas

0 1 2 3 4 5

Logic 0 Logic 1

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Computer Science Illuminated, Dale and Lewis

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Address decoder for 5 (01012)The output will be 1 if and only if the input is 01012

Address Decoders

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¾ Flip-flops are frequently used to store data

Digital Design, Mano

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¾ Bit : a binary digit that can have the value

0 or 1

memory in IBM PCs and compatibles

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¾ Execute information stored in memory

¾ Provide a means of communicating with CPU

¾ RAM (Random Access Memory) – temporary storage of programs that computer is running

¾ ROM (Read Only Memory) – contains programs and information essential to operation of the computer

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Address bus

Data buswww.elsolucionario.org

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¾ Carries information from place to place

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be unique

and the decoding circuitry finds the device

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INSIDE THE

COMPUTER

More about

Data Bus

better the CPU

¾ Think of data buses as highway lanes

expensive CPU and computer

¾ The average size of data buses in CPUs varies between 8 and 64

¾ To receive or send data

related to the size of its buses

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larger the number of devices that can

be addressed

CPU can communicate is always equal

regardless of the size of the data bus

¾ ex a CPU with 24 address lines and 16 data lines can provide a total of 224 or 16M bytes of addressable memory

¾ Each location can have a maximum of 1 byte of data, since all general-purpose CPUs are byte addressable

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the data must be stored in RAM or

memory

and permanent

¾ Tables or initialization program

permanent and can change with time

¾ Various versions of OS and application packages

¾ CPU gets information to be processed

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¾ In general, the more and bigger the registers, the better the CPU

is the increased cost of such a CPU

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Register A Register B

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¾ Performs arithmetic functions such as add, subtract, multiply, and divide, and logic

functions such as AND, OR, and NOT

¾ Points to the address of the next instruction to be executed

counter is incremented to point to the address

of the next instruction to be executed

¾ Interprets the instruction fetched into the CPU

instructions requires more transistors to design

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Assume that the code for the CPU to move a value to register A is B0H and the code for adding a value to register A is 04H

The action to be performed by the CPU is to put 21H into register A, and then add to register A values 42H and 12H

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Mem addr Contents of memory address

1400 (B0) code for moving a value to register A

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1. The program counter is set to the value 1400H,

indicating the address of the first instruction code to

be executed

2.

¾ The CPU puts 1400H on address bus and sends it

out

The memory circuitry finds the location

¾ The CPU activates the READ signal, indicating to

memory that it wants the byte at location 1400H

This causes the contents of memory location

1400H, which is B0, to be put on the data bus and brought into the CPU

以動畫表示

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¾ The CPU decodes the instruction B0

¾ The CPU commands its controller circuitry to bring

into register A of the CPU the byte in the next memory location

The value 21H goes into register A

¾ The program counter points to the address of the

next instruction to be executed, which is 1402H

Address 1402 is sent out on the address bus to

fetch the next instruction

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¾ From memory location 1402H it fetches code 04H

¾ After decoding, the CPU knows that it must add to

the contents of register A the byte sitting at the next address (1403)

¾ After the CPU brings the value (42H), it provides

the contents of register A along with this value to the ALU to perform the addition

It then takes the result of the addition from the

ALU’s output and puts it in register A

The program counter becomes 1404, the address

of the next instruction

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¾ Address 1404H is put on the address bus and the

code is fetched into the CPU, decoded, and executed

This code is again adding a value to register A

The program counter is updated to 1406H6.

¾ The contents of address 1406 are fetched in and

executed

¾ This HALT instruction tells the CPU to stop

incrementing the program counter and asking for the next instruction

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Chung-Ping Young

楊中平

8051 MICROCONTROLLERS

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TimerI/O

ROMRAM

Timer

purpose Micro- Processor

General-www.elsolucionario.org

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space are critical

¾ In many applications, the space it takes, the power it consumes, and the price per

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microprocessor (or microcontroller) to

do one task and one task only

¾ There is only one application software that

is typically burned into ROM

system, can be used for any number of applications

¾ It has RAM memory and an operating system that loads a variety of applications into RAM and lets the CPU run them

¾ A PC contains or is connected to various embedded products

it that performs only one task

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garage door openers, answering machines, fax machines, home computers, TVs, cable TV tuner, VCR, camcorder, remote controls, video games, cellular phones, musical instruments, sewing machines, lighting control, paging, camera, pinball machines, toys, exercise equipment

machines, microwave, copier, laser printer, color printer, paging

instrumentation, security system, transmission

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microprocessors have targeted their microprocessor for the high end of the embedded market

¾ There are times that a microcontroller is inadequate for the task

general-purpose microprocessor for the embedded market, it optimizes the processor used for embedded systems

interchangeably

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embedded system is to decrease power consumption and space

processors, the trend is to integrate more functions on the CPU chip and let designer decide which features he/she wants to use

high-end embedded applications

¾ Saves money and shortens development time

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microcontrollers made by various chip makers

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task at hand efficiently and cost effectively

¾ Speed

¾ Packaging

¾ Power consumption

¾ The amount of RAM and ROM on chip

¾ The number of I/O pins and the timer on chip

¾ How easy to upgrade to performance or lower power-consumption versions

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higher-Department of Computer Science and Information Engineering

tools, such as compilers, assemblers, and debuggers

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¾ The 8051 is an 8-bit processor

allowing other manufactures to make

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Bus Control

CPU

Ports

Serial Port

Etc.

Timer 0 Timer 1

On-chip RAM

On-chip ROM for code

P0 P1 P2 P3Address/Data

TXD RXD

External Interrupts

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¾ Add external ROM to it

¾ You lose two ports, and leave only 2 ports for I/O operations

32 32

32 I/O pins

2 3

2 Timers

128 256

128 RAM (bytes)

0K

8K 4K

ROM (on-chip program space in bytes)

8031 8052

8051 Feature

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¾ Flash (erase before write)

¾ Flash

on-chip flash via PC COM port

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¾ NV-RAM (changed one byte at a time), RTC (real-time clock)

of 8051

¾ ADC, DAC, extended I/O, and both OTP and flash

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Home Automation, Networking, and Entertainment Lab

Dept of Computer Science and Information Engineering National Cheng Kung University, TAIWAN

Chung-Ping Young

楊中平

8051 ASSEMBLY

LANGUAGE PROGRAMMING

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INSIDE THE

8051

Registers

temporarily, while the information could be

¾ a byte of data to be processed, or

¾ an address pointing to the data to be fetched

8-bit registers

¾ There is only one data type, 8 bits

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D0D1

D2D3

D4D5

D6D7

8 bit Registers

most significant bit

least significant bit

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PC PC (Program counter)

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operand

MOV A,#55H ;load value 55H into reg AMOV R0,A ;copy contents of A into R0

;(now A=R0=55H)MOV R1,A ;copy contents of A into R1

;(now A=R0=R1=55H)MOV R2,A ;copy contents of A into R2

;(now A=R0=R1=R2=55H)MOV R3,#95H ;load value 95H into R3

;(now R3=95H)MOV A,R3 ;copy contents of R3 into A

;now A=R3=95H

“#” signifies that it is a value

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“MOV A, #5”, the result will be A=05; i.e., A

= 00000101 in binary

Moving a value that is too large into a

If it’s not preceded with #,

it means to load from a memory location

Add a 0 to indicate that

F is a hex number and not a letter

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;to the accumulator

byte to register A and put the result in register A

immediate data, but the destination must always

be register A

“ADD R4, A” and “ADD R2, #12H” are invalid since A must be the destination of any arithmetic operation

ADD A, R2 ;add R2 to Accumulator

There are always

many ways to write

the same program,

depending on the

registers used

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Structure of

Assembly

Language

consisting of 0s and 1s

Assembly languages , which provided mnemonics for the machine code instructions, plus other features, were developed

of lines of Assembly language instructions

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¾ a mnemonic (abbreviation easy to remember)

to do with those items

¾ optionally followed by one or two operands

a series of statements, or lines

¾ Assembly language instructions

¾ Directives (or pseudo-instructions)

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8051

ASSEMBLY

PROGRAMMING

consists of four fields:

[label:] Mnemonic [operands] [;comment]

Mnemonics produce opcodes

Directives do not generate any machine code and are used only by the assembler

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program are outlines as follows:

1) First we use an editor to type a program,

many excellent editors or word processors are available that can be used

to create and/or edit the program

an ASCII file

the usual DOS conventions, but the source file has the extension “asm“ or “src”, depending

on which assembly you are using

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2) The “asm” source file containing the

program code created in step 1 is fed to

the extension for the list file is “lst”

3) Assembler require a third step called

linking

code files and produce an absolute object file with the extension “abs”

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4) Next the “abs” file is fed into a program

called “OH” (object to hex converter) which creates a file with extension “hex” that is ready to burn into ROM

step 2 through 4 into one step

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ASSEMBLER PROGRAM

LINKER PROGRAM

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very useful to the programmer

¾ It lists all the opcodes and addresses as well as errors that the assembler detected

¾ The programmer uses the lst file to find the syntax errors or debug

1 0000 ORG 0H ;start (origin) at 0

2 0000 7D25 MOV R5,#25H ;load 25H into R5

3 0002 7F34 MOV R7,#34H ;load 34H into R7

4 0004 7400 MOV A,#0 ;load 0 into A

5 0006 2D ADD A,R5 ;add contents of R5 to A

8 000A 80EF HERE: SJMP HERE;stay in this loop

address

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