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Microcontrollers

Class : 4th Semister E&C and EEESubject Code: 06ES42Chapter : UNIT 1-2Class : 2

Date : 15th Feb 2010

D R Subramanyam drs@slntech.com

Revision of Previous Class topics

Revision of Previous ClassMicroprocessor

Microcontroller

Difference between MP and MC

MC Architecture

RISC

CISC

Harvard

Von Newmann

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Microprocessors “A microprocessor is a multipurpose, programmable, clock

driven, register – based electronics device that reads binary instructions from a storage device called memory, accepts binary data as input and processes data according to those instructions and provides results as output”

• Example ： Intel’s x86, Motorola’s 680x0

CPU

General-Purpose Micro-processor

RAM ROM I/O Port

TimerSerial COM Port

Data Bus

Address Bus

General-Purpose Microprocessor System

Many chips on mother’s board

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Microcontroller:

• A smaller computer• On-chip RAM, ROM, I/O ports...• Example ： Motorola’s 6811, Intel’s 8051, Zilog’s Z8X and PIC 16X

RAM ROM

I/O Port

TimerSerial COM Port

Microcontroller

CPU

A single chip

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Microprocessor vs Microcontroller

Microprocessor

• CPU is stand-alone, RAM, ROM, I/O, timer are separate

• designer can decide on the amount of ROM, RAM and I/O ports.

• expensive• versatility • general-purpose

Microcontroller

• CPU, RAM, ROM, I/O and timer are all on a single chip

• fix amount of on-chip ROM, RAM, I/O ports

• for applications in which cost, power and space are critical

• single-purpose

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RISC (Reduced Instruction Set Computing Processor)

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CISC (Complex Instruction Set Computing Processors)

• Numerous Instruction Group• Numerous Addressing Modes• Microcoded Instructions• Microcontrollers and Microprocessors are

CISC based.• DSP’s are closer to RISC.

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Von Newmann Architecture

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Harvard Architecture

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Let us know more about Microcontrollers

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Microcontroller’s internal Blocks

• CPU ( ALU, Registers, Oscillator/clock, Bus control)• RAM /Data memory• ROM / program memory• I/O ports• Timer/counters• Serial ports• Interrupts

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Let us put together all what we discussed

Microcontroller Block Diagram

CPU

On-chip RAM

On-chip ROM for program code

4 I/O Ports

Timer 0

Serial PortOSC

Interrupt Control

External interrupts

Timer 1

Timer/Counter

Bus Control

TxD RxDP0 P1 P2 P3

Address/Data

Counter Inputs

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Microcontroller Block Diagram

ALU

Internal ROM

I/O Ports

Internal RAM

AccumulatorRegisters

Program CounterStack Pointer

Oscillator

Counter/Timer

Serial Port

Interrupt Logic

Bus Control

The 8051 Oscillator and Clock

Program Counter and Data pointer

Program Counter (PC):

Program counter is a 16 bit Register. It holds the address of the next instruction to be executed.

It does not have internal address (PC is the only register not having the internal address)

Data Pointer (DPTR): DPH and DPL

DPTR is used to furnish memory address for internal and external code access and external data access

A and B CPU Registers

• A and B registers are the two registers among the 34 general purpose registers

• Holds results of many instructions, particularly math and logical operations

• A register (Accumulator) is the most versatile and is used for many operations including addition, subtraction, integer multiplication and division and Boolean bit manipulations

• A register is also used for all data transfer between 8051 and any external memory

• B register is used with A register for multiplication and division operations.

Flags and Program Status Word (PSW)

Internal MemoryInternal RAM - 128 bytes 00H to 7FHInternal ROM - 4 K Bytes 000H to FFFH

Internal RAM

The Stack and Stack pointer(SP)Stack area:Part of Internal RAMIt is limited in height to the size of internal RAM

Stack Pointer (SP): 8 bits wideIncrements unlike many microprocessors where SP decrementsOn RESET it is et to 07H

The Stack and Stack pointer(SP)

Special Function Registers(SFRs)

Special Function Registers(SFRs)

Note: Program Counter Register is not a special function Register

Special Function Registers

Special Function Registers-Continued

Internal ROM

Input / Output Pins, Ports and Circuits

A Pin of Port 1

8051 IC

D Q

Clk Q

Vcc

Load(L1)

Read latch

Read pin

Write to latch

Internal CPU bus

M1

P1.X pinP1.X

TB1

TB2

P0.x

Writing “1” to Output Pin P1.X

D Q

Clk Q

Vcc

Load(L1)

Read latch

Read pin

Write to latch

Internal CPU bus

M1

P1.X pinP1.X

8051 IC

2. output pin is Vcc1. write a 1 to the pin

1

0 output 1

TB1

TB2

Writing “0” to Output Pin P1.X

D Q

Clk Q

Vcc

Load(L1)

Read latch

Read pin

Write to latch

Internal CPU bus

M1

P1.X pinP1.X

8051 IC

2. output pin is ground1. write a 0 to the pin

0

1 output 0

TB1

TB2

Reading “High” at Input Pin

D Q

Clk Q

Vcc

Load(L1)

Read latch

Read pin

Write to latch

Internal CPU bus

M1

P1.X pin

P1.X

8051 IC

2. MOV A,P1

external pin=High1. write a 1 to the pin MOV

P1,#0FFH

1

0

3. Read pin=1 Read latch=0 Write to latch=1

1

TB1

TB2

Reading “Low” at Input Pin

D Q

Clk Q

Vcc

Load(L1)

Read latch

Read pin

Write to latch

Internal CPU bus

M1

P1.X pin

P1.X

8051 IC

2. MOV A,P1

external pin=Low1. write a 1 to the pin

MOV P1,#0FFH

1

0

3. Read pin=1 Read latch=0 Write to latch=1

0

TB1

TB2

Other Pins

• P1, P2, and P3 have internal pull-up resisters.– P1, P2, and P3 are not open drain.

• P0 has no internal pull-up resistors and does not connects to Vcc inside the 8051.– P0 is open drain.– Compare the figures of P1.X and P0.X.

• However, for a programmer, it is the same to program P0, P1, P2 and P3.

• All the ports upon RESET are configured as output.

A Pin of Port 0

8051 IC

D Q

Clk Q

Read latch

Read pin

Write to latch

Internal CPU bus

M1

P0.X pinP1.X

TB1

TB2

P1.x

Input/Output Pins, Ports and CircuitsControl Signals

Address/Data

Input/Output Pins, Ports-PORT0

Control Signals

Address/Data

Input/Output Pins, Ports-PORT1

Input/Output Pins, Ports-PORT2

Input/Output Pins, Ports-PORT3

External Memory

External Memory Timing Wave Forms

Counters and Timers

Timer :

Counting

TCON-Timer Control SFR

TCON-Continued

TMOD-Timer Mode Control SFR

Timer/Counter Control Logic

Timer Modes of Operation

Timer Mode 0

Timer Mode 1

Timer Mode 2

Timer Mode 3

Timer Mode 0

13 Bit Timer/CounterTHx - 8 bit Register and TLx – 5 bit Register

Timer Mode 1

16 Bit Timer / counterTMOD = 01bThe Timer Flag would be set in 1311 seconds using a 6 MHz Crystal

Timer Mode 2

This mode exhibits auto reload feature

Timer Mode 3

Timer 1 can still be used but interrupt feature can not be used

Serial Data Input/Output

Registers used for Serial CommunicationSBUF-Serial Buffer registerSCON-Serial Control registerPCON-Power Control register

SCON-Serial Port Control SFR

PCON-Power Mode Control SFR

Serial Communication Continued

Serial InterruptsData Transmission Data Reception

Baud rate is set using Timer 1Whenever serial port is used in Mode 1 or 3 Timer 1 can not be used for any other purpose other than generating Baud clock

Shift Register Mode 0 Timing

Standard UART data word

Multi Processor Data Word

Interrupt :

Interrupts

1. Enabling and Disabling Interrupts

2. Interrupt Priority

3. Writing the ISR (Interrupt Service Routine)

IE register

IP register

Interrupt VectorsInterrupt Vector Address

System Reset 0000H

External 0 0003H

Timer 0 000BH

External 1 0013H

Timer 1 001BH

Serial Port 0023H

Timer 2 002BH

Reset

Summary

8051 µC Hardware