8051 Microcontroller

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Intel’s

8051

Micro controller

Basics
What are Micro controller's ? Why the name Micro controller ? Basically used for control actions.It is used to control the operation of machine using fixed program that is stored in ROM/EPROM and that does not change over the life time.

What is MCS 51 ?

Why to study 8051 ?
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Features of 8051
8 bit ALU. 16 bit PC and DPTR. 8 bit stack pointer and 8 bit PSW. 4K internal ROM 128 bytes of Internal RAM. 32 bits arranged as four,8 bit ports P0-P3. Two 16 bit timer/counters, T0 & T1. Full duplex serial Port. August 28, 2008 Y.H.Dandawate 4

Features contd…
Control Registers TCON,TMOD,SCON,PCON,IP,IE etc (SFR’s). Two External and three internal interrupt sources. 0-12 MHz clock. 40 pin DIP package. Works in Power Down and Idle mode. Powerful Instruction set. August 28, 2008 Y.H.Dandawate 5

Block Diagram of 8051.

Pin Diagram of 8051

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Internal RAM Organization

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Internal RAM Organization

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Clock for 8051.

Tin = N * 12 / Clk.Freq

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Program Status Word (PSW)
7
CY

6
AC

5
F0

4

3

2

1

0
P

RS1 RS0 OV ---

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I/O Ports of 8051-Port 0

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I/O Ports of 8051-Port 1

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I/O Ports of 8051-Port 2

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I/O Ports of 8051-Port 3

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Memory Interfacing with 8051
How to interface Program memory(EPROM) up to 64 KB to 8051 ? How to interface Data memory(RAM) upto 64 KB to 8051 ? How 8051 distinguishes Program and data memory operations ?

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Timer Control Register (TCON)
7
TF 1

6
TR1

5
TF0

4
TR0

3
IE 1

2
IT1

1
IE0

0
IT 0

TF1 :Vector location 001B H. TF 0: Vector location 000B H IE 1 : Vector location 0013 H IE 0: Vector location 0003 H August 28, 2008 Y.H.Dandawate 22

Timer Mode (TMOD)
7
Gate

6
C/T

5
M1

4
M0

3
Gate

2
C/T

1
M1

0
M0

Timer 1

Timer 0

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Modes of Timer/Counter
Mode Mode Mode Mode 0 1 2 3 : : : : 5 bit prescaler (13 bit ) 16 bit timer 8 bit Auto reload TL 0 and TH0 are independent but TH0 controlled by TR1 and TF1.

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Serial Input/Output
Registers used are SCON and SBUFF. There are physically two SBUFF registers having same address i.e 99 H. Interrupt is generated whenever data is transmitted and received. Controller goes to execute ISR for serial communication from 0023h. August 28, 2008 Y.H.Dandawate 25

Serial Control (SCON) register
7
SM0

6

5

4

3

2

1
RB8

0
TI RI

SM1 SM2

REN TB8

SMO SM1 0 0 0 1 1
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1 0 1

Shift register mode baud=1/12 8 bit UART baud=variable 9 bit UART baud= f/32 or f/64 9 bit UART baud = variable Y.H.Dandawate 26

Power Control (PCON) Register
7
SMOD

6
-

5
-

4

3
GF1

2
GF0

1
PD

0
IDL

IDLE Mode :The internal clock is gated off to the CPU,but not to the timer,serial port and all registers maintain the data. POWER DOWN :On chip oscillator is stopped.But RAM and SFR’s are held. August 28, 2008 Y.H.Dandawate 27

Idle and Power Down Hardware

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Interrupt Enable (IE) Register
7
EA

6
--

5
ET2

4
ES

3
ET1

2
EX1

1
ET0

0
EX0

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Interrupt Priority (IP) Register
7
--

6
--

5
PT2
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