PIC

MICROCONTROLLERS

Peeyush.K.P.

ASE Ettimadai

What is an Embedded System?

Communication

Avionics

2

Consumer

Electronics

Automobile

Household Appliances

Office Equipments

System in which software is embedded into the

hardware ( firmware).

The core part of the system will be a programmable device.

What is an Embedded system?

The core part of the system will be a programmable device.

Automotive Embedded Systems

� Today’s high-end automobile have > 80

microprocessors:

� 4-bit microcontroller checks seat belt;

� microcontrollers run dashboard devices;

� 16/32-bit microprocessor controls engine.

4

� 16/32-bit microprocessor controls engine.

� Millions lines of code

Vending Machines

5

Sojourner

6

GPS Receivers

7

� Reduced number of components.

� Reduced size.

� Reduced cost.

� Reduced power consumption.

Why Embedded systems?

� Easier upgradation.

� Easier troubleshooting & maintenance.

� Best suited for specific controlling applications.

Why uC?

� Microprocessor:• Requires ‘external’ support hardware

• E.g., External RAM, ROM, Peripherals.

• Application:Processing-Arithmetic,logic operations.

� Microcontroller:Very little external support hardware/Stand alone.• Very little external support hardware/Stand alone.

• Most RAM, ROM and peripherals on chip.

• “Computer on a chip”, or “System on chip” (SOC)

• E.g., PIC = Peripheral Interface Controller

• Application: Controlling purposes.

Microcontroller

VARIOUS MICROCONTROLLERS

� 8 bit microcontrollers

� Microchip - PIC 12 & 16 Series.

� Atmel - 89c51

� Intel - 8051

� Motorola - 68HCxx series

� 16 bit microcontrollers

� Microchip - PIC 18 series

� 32 bit microcontrollers

� ARM Processors

� DSP based microcontrollers

� Shark

Two Different Architectures

RISC vs. CISC

� Reduced Instruction Set

Computer (RISC)

� Used in: SPARC, ALPHA,

Atmel AVR, etc.

� Few instructions

� Complex Instruction Set

Computer (CISC)

� Used in: 80X86, 8051,

68HC11, etc.

� Many instructions� Few instructions

(usually < 50)

� Only a few addressing

modes

� Executes 1 instruction in 1

internal clock cycle (Tcyc)

� Many instructions

(usually > 100)

� Several addressing modes

� Usually takes more than 1

internal clock cycle (Tcyc)

to execute

WHY PIC ?WHY PIC ?

WHY PIC ?

� PICs use the Harvard Architecture

� PICs and most Harvard chips are “RISC”

� 35 Instructions

Executes 1 instruction in 1 internal clock cycle � Executes 1 instruction in 1 internal clock cycle

� In-Circuit Serial Programmable (ICSP) – via two pins.

� Available in different packages

Features

� Power On Reset Timer

� Oscillator Startup Timer

� WatchDog Timer

Sink/Source Current – 25ma� Sink/Source Current – 25ma

� Flash Programming

POR/Oscillator Startup Timer

WatchDog Timer

00

01

02

..

....

FF

00

Roll Over

Sink/Source Current – 25ma

The PIC Family: Cores

PICs come with 1 of 3 CPU ‘cores’:

The Base-line : 12bit cores with 33 instructions.

Eg:12C50x, 12C67x

The Mid-Range : 14bit cores with 35 instructions. Eg:16C5x,16Cxxx

The High-End : 16bit cores with 58 instructions.

Eg:17C4x,17C7xx

‘Enhanced’ 16bit cores with 77 instructions: 18Cxxx

Areas of Application.

� Base-line

� Inexpensive controllers, glue logic, simple tasks.

� E.g., quadrature decoding, digital interfacing.

� Mid-range

� Multitasking programs, serial communication.

� E.g., Cheap data acquisition system and digital I/O � E.g., Cheap data acquisition system and digital I/O system for PC off COM ports, data logging.

� High-end

� RTOS, low end DSP, communications, big moosey applications.

� E.g., FEC converter, Rocket Flight Computer, cheap FFT chip.

ProgramMemory (ROM)-size

PIC program space is different for each chip.

Some examples are:

12C508 512 12bit instructions

16C71C 1024 (1k) 14bit instructions

16F877 8192 (8k) 14bit instructions

17C766 16384 (16k) 16bit instructions

ProgramMemory (ROM)-types

PICs have two different types of program storage:

EPROM (Erasable Programmable Read Only Memory)

Needs high voltage from a programmer to program (~13V)(~13V)

Needs windowed chips and UV light to erase

Note: One Time Programmable (OTP) chips are EPROM chips, but with no glass window. ( ‘CR’ )PIC Examples: Any ‘C’ part: 12C50x, 17C7xx, etc.

ProgramMemory (ROM)-types.

FLASH

Re-writable (even by chip itself)

Much faster to develop on! Much faster to develop on!

Finite number of writes (~100k Writes)

PIC Examples: Any ‘F’ part: 16F84, 16F87x,

18Fxxx (future)

Data Memory (RAM-volatile)

PICs use general purpose “file registers” for RAM (each

register is 8bits for all PICs)

Some examples are:

12C508 25 Bytes RAM12C508 25 Bytes RAM

16C71C 36 Bytes RAM

16F877 368 Bytes

17C766 902 Bytes RAM

Data Memory (EEPROM non-volatile)

� For permanent storage of data.

� Available in few PICs only.

Eg:16F8X,12CE5XX,16F87X� Eg:16F8X,12CE5XX,16F87X

Speed

PICs require a clock to work.

Can use crystals, clock oscillators, or even an RC circuit.

Some PICs have a built in 4MHz RC clock

- Not very accurate, but requires no external components!

Instruction speed = 1/4 clock speed (Tcyc = 4 * Tclk) Instruction speed = 1/4 clock speed (Tcyc = 4 * Tclk)

All PICs can be run from DC to their maximum spec’d speed:

12C50x 4MHz

12C67x 10MHz

16Cxxx 20MHz

17C4x /17C7xxx 33MHz

18Cxxx 40MHz

Peripherals

Different PICs have different on-board peripherals

Some common peripherals are:

� Tri-state (“floatable”) digital I/O pins.

� Analog to Digital Converters (ADC) (8, 10 and � Analog to Digital Converters (ADC) (8, 10 and 12bit, 50ksps).

� Serial communications: UART (RS-232C), SPI, I2C, CAN.

� Pulse Width Modulation (PWM) (10bit).

� Timers and counters (8 and 16bit).

� Watchdog timers, Brown out detect, LCD drivers.

Packages

PICs come in a huge variety of packages:

8 pin DIPs, SOICs: 12C50x (12bit) , 12C67x (14bit)

18pin DIPs, SOICs: 16C5X (12bit), 16Cxxx (14bit)

28pin DIPs, SOICs: 16C5X (12bit), 16Cxxx (14bit)28pin DIPs, SOICs: 16C5X (12bit), 16Cxxx (14bit)

40pin DIPs, SOICs: 16Cxxx (14bit), 17C4x (16bit)

44 - 68pin PLCCs*: 16Cxxx (14bit), 17Cxx (16bit)

Commonly used mid range series

PICs

� The 16F8x series- 16F84.

� The 16F7x series- 16F73,74,76,77.

� The 16F87x series- 16F873, 874,876,877.

Comparison of Commonly Used

Mid range series of PIC

882Stack levels

200ns200ns400ns

20MHz20MHz10MHz

Operating Speed

Clock input

Instruction cycle

87X7X16f8X

11NoSSP/SPI/I2C

YesYesNoInterrupt on Pin Change

11NoUSART/SCI

8bit X 2 + 16bit X 18bit X 2 + 16bit X 18bit X 1Timers

22NoCCP modules

10bit8bitNoADC

882Stack levels

YesNoYesData EEPROM

Comparison of Commonly Used

Mid range series of PIC

A,B

18

83

A,B,C,D,EA,B,CA,B,C,D,EA,B,CA,BI/O Ports

4028402818Total pins

77/87776/87674/87473/87384

YesYesYesYesNoNoBOR

8585NANAADC channels

YesNoYesNoNoNoPSP

2562561281286464EEPROM

36 B

512 B

13

368 B368 B192 B192 B 68 BData m/y

8 KB8 KB4 KB4 KB1 KBProg. m/y

3322332213I/O Pins

PIC 16F874/877

PIC 16F874/877

PIN DIAGRAM

PIC16F877A Block Diagram

Instruction

Bus

Must be

involved in all

arithmetic

Data Bus

Data

Memory

Instruction

Memory

Most

important

register in

the PIC

arithmetic

operations

PIC16F877A Memory

� The PIC16F877A has an 8192 (8k) 14bit instruction

program memory

� 368 Bytes Registers as Data Memory :

�Special Function Registers: used to control peripherals �Special Function Registers: used to control peripherals

and PIC behaviors

�General Purpose Registers: used to a normal

temporary storage space (RAM)

� 256 Bytes of nonvolatile EEPROM

PIC16F877A Memory Map

www.greytechnologies.net

SFR

INSTRUCTION SET

1) Move Literal Value To Work RegisterSyntax : MOVLW <LITERAL>

Eg: MOVLW 0X02

2) Move Content of Work Reg. To File Reg. Syntax : MOVWF <FILE REG>Syntax : MOVWF <FILE REG>

Eg : MOVWF PORTA

3) Move Content of File Reg. To Desti.Syntax : MOVF <FILE REG>,<DESTI.>

Eg : MOVF PORTA,0

Eg : MOVF PORTA,1

INSTRUCTION SET

1) Bit Set File RegisterSyntax : BSF <File Reg>,<Bit>

Eg: BSF PORTA,1

2) Bit Clear File RegisterSyntax : BCF <File Reg>,<Bit>Syntax : BCF <File Reg>,<Bit>

Eg : BCF PORTA,1

INSTRUCTION SET

1) Bit Test File Register Skip if SetSyntax : BTFSS <File Reg>,<Bit>

Eg: BTFSS PORTA,1

2) Bit Test File Register Skip if ClearSyntax : BTFSC <File Reg>,<Bit>Syntax : BTFSC <File Reg>,<Bit>

Eg : BTFSC PORTA,1

INSTRUCTION SET

1) Decrement File Register Skip if ZeroSyntax : DECFSZ <File Reg>,<Desti.>

Eg: DECFSZ COUNT,1

2) Increment File Register Skip if ZeroSyntax : INCFSZ <File Reg>,<Desti.>Syntax : INCFSZ <File Reg>,<Desti.>

Eg : INCFSZ COUNT,1

Programming PIC

Basic Circuit

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