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8/8/2019 Pic.tpt Iete

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INTRODUCTIONINTRODUCTIONTOTO

PIC MICROCONTROLLERSPIC MICROCONTROLLERS

Dr. Y.Narasimha Murthy Ph.DSRI SAIBABA NATIONAL COLLEGE(AUTONOMOUS)SRI SAIBABA NATIONAL COLLEGE(AUTONOMOUS)

ANANTAPURANANTAPUR--515001515001--A.PA.P--INDIAINDIA

[email protected]@yahoo.com


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Do you Know this gentleman ???..


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None other than Steve Sanghi, the chairman,president and CEO ofMicrochip Technology

Inc.

Sanghi moved from India to U.S. to pursue a

Masters degree at the University of

Massachusetts after bachelors degree in

engineering, from Punjab Engineering College.

In 1993, Sanghi became president and CEO of

Microchip after seeking advice from venture

capital firms on starting his own company.


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Since then, he has transformed Microchip

into a billion-dollar company specializing inMicrocontroller and analog semiconductors

used in devices ranging from remote

controls to cars. He also has been involved

in science and technology education

programs, and hes been known to frequent

science fairs and question kids about their

projects.


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Brief Introduction.Brief Introduction.

The term PIC stands for PeripheralInterface Controller .It is the brain child of

Microchip Technology, USA .They havecoined this name to identify their single

chip micro-controllers. These 8-bit micro

controllers have become very important

now -a -days in industrial automation andembedded applications etc..


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PICs are popular with both industrial

developers and hobbyists alike due to theirlow cost, wide availability, large user base,

extensive collection of application notes,

availability of low cost or free development

tools, and serial programming (and re-

programming with flash memory)

capability.


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Microchip PIC microcontrollers are

available in various types. When PICmicrocontroller MCU was first availablefrom General Instruments in early 1980's,the micro-controller had a simple

processor executing 12-bit wideinstructions with basic I/O functions. Thesedevices are known as low-endarchitectures. They have limited programmemory and are meant for applicationsrequiring simple interface functions andsmall program & data memories.


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Some of the lowSome of the low--end device numbers areend device numbers are

12C5XX

16C5X 16C505


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Mid range PIC architectures

built by upgrading low-end architectureswith more number of peripherals, more

number of registers and more

data/program memory.

Some of the mid-range devices are

16C6X

16C7X

16F87X


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Program memory type is indicated by analphabet.

C = EPROM

F = Flash

RC = Mask ROM


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28/40-Pin 8-Bit CMOS FLASHMicrocontrollers Core Features:

High performance RISC CPU Only 35 single word instructions to learn

All single cycle instructions except for program

branches which are two cycle

Operating speed: DC - 20 MHz clock input DC - 200 ns instruction cycle

Up to 8K x 14 words of FLASH ProgramMemory,

Up to 368 x 8 bytes of Data Memory (RAM) Up to 256 x 8 bytes of EEPROM Data Memory


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Pin-out compatible to the PIC16C73B/74B/76/77

Interrupt capability (up to 14 sources) Eight level deep hardware stack

Direct, indirect and relative addressing modes

Power-on Reset (POR)

Power-up Timer (PWRT) and

Oscillator Start-up Timer (OST)

Watchdog Timer (WDT) with its own on-chip RC

oscillator for reliable operation


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Programmable code protection

Power saving SLEEP mode

Selectable oscillator options Low power, high speed CMOS FLASH/EEPROM

technology

Fully static design

In-Circuit Serial Programming (ICSP) via twopins

Single 5V In-Circuit Serial Programming capability

In-Circuit Debugging via two pins

Processor read/write access to program memory Wide operating voltage range: 2.0V to 5.5V

High Sink/Source Current: 25 mA


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Commercial, Industrial and Extended

temperature

ranges

Low-power consumption:

- < 0.6 mA typical @ 3V, 4 MHz

- 20 A typical @ 3V, 32 kHz

- < 1 A typical standby current


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Salient featuresSalient features

Speed :

When operated at its maximum clock ratea PIC executes most of its instructions in

0.2 Qs or five instructions permicrosecond.

Instruction set Simplicity :

The instruction set is so simple that itconsists of just 35 instructions


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Integration of operational features:

Power-on-reset and brown-out

protection ensure that the chip operatesonly when the supply voltage is withinspecifications. A watch dog timer resetsthe PIC if the chip malfunctions or

deviates from its normal operation at anytime.

Programmable timer options:

Three timers can characterize inputs,control outputs and provide internaltiming for the program execution.


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Powerful output pin control:

A single instruction can select and drivea single output pin high or low in its 0.2

Qs instruction execution time. The PIN

can drive a load of up to 25QA.

I/O port expansion:

With the help of built in serial peripheral

interface the number of I/O ports can be

expanded. EPROM/DIP/ROM optionsare provided.


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I/O port expansion:

This is the most important aspect in thePIC controllers.With the help of built in

Serial Peripheral Interface(SPI) the

number of I/O ports can be expanded.

EPROM/DIP/ROM options are provided.

Interrupt control:

Up to 12 independent interrupt sources

can control when the CPU will deal witheach sources.


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PIC 16C6X/7X CONTROLLERS

PERIPHERAL FEATURES The PIC16CXX/17CXX is a family of low-cost,

high-performance, CMOS, fully-static, 8-bitmicrocontrollers.

There are Three Timers : Namely Timer 0,Timer 1, Timer 2

Timer 0: 8-bit timer/counter with 8-bit prescaler

Timer 1: 16-bit timer/counter with prescaler canbe incremented during sleep via external

crystal/clock Timer 2: 8-bit timer/counter with 8-bit period

register, pre-scaler and post-scaler


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ContdContd

Capture/Compare/PWM (CCP) module(s)

Capture is 16-bit, max resolution is 12.5

ns, Compare is 16-bit, max resolution is

200ns, PWM max resolution is 10-bit Synchronous Serial Port (SSP) with SPITM

and I2C

Universal Synchronous AsynchronousReceiver Transmitter (USART/SCI)


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Parallel Slave Port (PSP) 8-bits wide, withexternal RD, WR and CS controls

Brown-out detection circuitry for Brown-out

Reset (BOR)

PIC16CXX microcontroller family has

enhanced core features, eight-level deep

stack, and multiple internal and external

interrupt sources.


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ARCHITECTUREARCHITECTURE

The high performance of the PIC16CXX familycan be attributed to a number of architectural

features commonly found in RISC

microprocessors. To begin with, the PIC 16CXX

uses a Harvard architecture, in which, programand data are accessed from separate memories

using separate buses. This improves bandwidth

over traditional Von Neumann architecture

where program and data may be fetched fromthe same memory using the same bus.


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HARVARD ARCHTECTUREHARVARD ARCHTECTURE


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As the PIC 16c6x/7x family of micro-controllers

uses Harvard Architecture it enables thedevices exceptionally fast execution speed for agiven clock rate. In the Harvard Architectureseparate buses are used for Data and

Instruction as shown in the diagram.

Instructions are fetched from program memoryusing buses that are distinct from the buses

used for accessing variables in data memory,I/O ports etc. Every instruction is coded as asingle 14-bit word and fetched over a 14-bit widebus.


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ContdContd..

Separating program and data buses

further allows instructions to be sized

differently than 8-bit wide data words.

Instruction op-codes are 14-bits wide

making it possible to have all single word

instructions. A 14-bit wide program

memory access bus fetches a 14-bitinstruction in a single cycle


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ExampleExample::

The PIC 16C61 addresses 1K x 14 ofprogram memory.

The PIC16C62/62A/R62/64 addresses 2Kx 14 of program memory, and

the PIC16C63/R63/65/65/65A/R65devices address 4K x 14 of programmemory.

The PIC 16C66/67 address 8K x 14program memory. All program memory isinternal.


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The PIC16CXX can directly or indirectly address

its register files or data memory. All special

function registers including the program counter

are mapped in the data memory. The PIC16CXX

has an orthogonal (symmetrical) instruction setthat makes it possible to carry out any operation

on any register using any addressing mode. This

symmetrical nature and lack of special optimal

situations makes programming with thePIC16CXX simple yet efficient, thus significantly

reducing the learning curve.


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Block DiagramBlock Diagram--16C6X16C6X


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CPU REGISTERSCPU REGISTERS

The CPU registers are

Working Register (W)

Status Register FSR File Select Register

INDF

PCLATH

Program Counter

PCL

Eight Level Stack


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General Block DiagramGeneral Block Diagram


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ContdContd

Working Register:

Working Register is used by many instructions

as the source of an operand. It also serves as

the destination for the result of instructionexecution and it is similar to accumulator in

otherQcs and Qps. It is a 8-bit regarding.

Status Register:

It contains the arithmetic status of the ALU, theRESET status and the bank select bits for the

data memory.


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C: Carry/borrow bit

DC: Digit carry/borrow bit

Z: Zero bitNOT_PD: Reset Status bit (Power-down

mode bit)

NOT_TO: Reset Status bit (tme- out bit)

RPO: Register bank SelectThe bits 7 and 6 of Status Register are unused by

16c6x/7x.


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The C bit is set when two 8-bit operandsare added together and a 9-bit result

occurs. This 9-bit is placed in the carry bit.

The DC or Digit carry bit indicates that a

carry from the lower 4 bits occurred during

an 8-bit addition.

ContdContd


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Example: 0011 1000

0011 10000111 0000

Here DC=1 as a result of the carry fromthe bit 3 to the bit 4 position.


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The Z or zero bits is affected by the execution of

arithmetic or logic instructions.

The reset status bits NOT_TO and NOT_PD are

used in conjunction with PICs sleep mode. Themicro controller can put itself to sleep mode to

save power during intervals when it has nothing

to do. It can be reset by any of three kinds. Upon

reset the CPU can check these two reset statusbits to determine which kind of event resettled it

and then respond accordingly.


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The Register bank select bit RPO is usedto select either bank .

When RPO=0, select Bank 0, RPO=1,

select Bank 1.

Example: bcf STATUS, RPO

Select bank 0

bsf STATUS, RPO

Select bank 1.


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ContdContd

FSR (File Select Register):It is the pointer used for indirect addressing. Inthe indirect addressing mode the 8-bit registerfile address is first written into FSR. It is a

special purpose register that serves as anaddress pointer to any address through out theentire register file.

INDF (Indirect File):

It is not a physical register .Addressing thisINDF will cause indirect addressing. Anyinstruction using the INDF register actuallyaccess the register pointed to by the FSR.


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ContdContd

PCL:PCL is actually the lower 8-bits of the 13-bit

program counter. It can be read like any other

register.

PCLATH (Program Counter Latch):

The upper 3-bits of PCLATH remains zero and

serves no purpose, it is only when PC2 is

written to that PCLATH is automatically written

into the PC at the same time.


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Memory organisation :

It has three memory blocks.

Program memory

Data memory Stack

P MP M


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The 6x/7x family controllers have either 2k or 4k

address of program memory. Normally aprogram memory of 2k addresses needs only a

11-bit program counter to access any address

(211=2048=2k).

A program memory of 4k address needs a 12-

bit program counter. But this PIC family uses

13-bit program counter allowing the controllers

to an 8k-program memory without changing the

CPU structure.

Program MemoryProgram Memory


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Two addresses in the program memory

address space are treated in a special wayby the CPU. The first address H 000 being

a go to mainline instruction the second

special address, H 004 being a go to in

service instruction can be assigned to thisaddress to make the CPU to jump to the

beginning of the Interrupt Service routine

located elsewhere in the memory space.


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When we deal with tables, if any tables are

created they are assigned to addresses in

the range H005 H0FF. For most of the

applications this space is sufficient.

The main line program begins after the

tables.


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Data memory (Register Files):Data memory (Register Files):

Data Memory is also known as RegisterFile. Register File consists of two

components.

General purpose register file ( RAM). Special purpose register file (similar to

SFR in 8051).


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The special purpose register file consists

of input/output ports and control registers.Addressing from 00H to FFH requires 8

bits of address. However, the instructions

that use direct addressing modes in PIC to

address these register files use 7 bits of

instruction only. Therefore the register

bank select (RP0) bit in the STATUS

register is used to select one of theregister bank


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Data Memory mapData Memory map


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PIC Reset actionsPIC Reset actions

Reset is used to put themicrocontroller into a known state.Normally when a PIC microcontrolleris reset, execution starts from

address 0 of the program memory.This is where the first executable userprogram resides. The reset actionalso initializes various SFR registersinside the Microcontroller.


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ContdContd

Reset mechanisms ensure that the CPU startsrunning when the appropriate operatingconditions have been met, and can be used torestart the CPU in case of program failure.

The actual reset to the CPU or the Chip_Reset,is generated by a flip-flop. This has two inputs, S

(Set) and R (Reset).


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Contd..Contd..

The CPU enters Reset mode when Chip_Resetgoes low, which is caused by the S line going

high. It stays there until the flip-flop is cleared,

caused by the R line going high.

The S input to the flip-flop goes high, via a three-

input OR gate, if any of the following goes high:


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Contd..Contd..

The Reset action normally occurs invarious situations like

Power On Reset

Master Clear( ) Reset Watchdog Timer Reset

Brown-out Reset (This feature is not

available in PIC16C61/62/64/65 series.Only 74 series have this feature


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Contd..Contd..

The reset action will set the program

counterto the starting address of the

program.This starting address is different

for different members.For Ex:Starting

address for PIC16C71 is 000H.whereas for

PIC16C57 it is 7FFH.

So,The first instruction to be executed willappear at the reset vector.


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An important point to be remembered, is

when powered ,most of the hardware

registers are initialized ,but RAM locations

are not initialized.A reset cycle will

initialize the RAM locations.

So,the conclusion is Reset and Power-on

are different in PIC controllers.


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Contd..Contd..

The Brown-out reset occurs when thesupply voltage falls below 4 volts.Thedevice remains in the Brown-out resetstate till the supply voltage is restored.The

Brown-out reset also includes anotherfeature .If Vdd is hit with a transient noisespike ,causing Vdd to drop below 4.0Voltsfor longer than 100 micro seconds theBrown-out reset circuit detects that andreset the


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Contd..Contd..

chip.whereas in most of the other microcontrollersmany erroneous executions takes place during this

time.The PIC brown-out reset will also help if the

power-on reset conditions are not not met.

There is a provision of power-up timer of about72mS.Once this is enabled the Brown-out reset

occurs once again incase of non-restoration of

supply within 72 mS


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PIC Oscillator ConnectionsPIC Oscillator Connections

There are 4 common oscillator modes that areavailable on most PIC micro devices.

HS, XT, LP and RC. (High speed, Crystal, Low-

power clocking, Internal RC)

These modes support crystals, canned oscillatormodules, some resonators or the use of an

external resistor and capacitor as a clocksource. When using a crystal or resonator, othercomponents such as capacitors may be needed.


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Contd..Contd..

The HS mode stands for High Speed mode. Itis designed to be used with crystals,andresonators with a frequency of 3 to 4 MHz ormore. The important thing to remember about

HS mode is that it provides the highest drivelevel available.

Crystals and Resonators must be DRIVEN by asignal to work. The gain on this signal controls

whether an oscillation will occur and how strongit will be. Care must be taken not to underdriveor overdrive the crystal or resonator.


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Contd..Contd..

The XT mode stands for Crystal mode and willproduce a medium drive level. It is designed tobe used with crystals and resonators of 1 toabout 4 MHz.

XT mode has moderate power consumptionsince its drive level is lower than that of

HS mode, and because a lower clock speed isproduced. Remember, as a rule: the

faster the clock used, the more current theapplication will require


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Contd..Contd..

The LP mode stands for "Low Power mode.This mode is useful for circuits that require thelowest power possible. LP mode is engineeredfor 32.768kHz crystal operation, and it canfunction at any frequency below 200kHz. LPmode is most commonly used for 32.768kHzoperation.

LP mode will produce the slowest clock rate,and as a result, the lowest power consumption

of all the modes. LP mode is ideal for timing sensitive applications

since these same crystals are used as a timebase in wrist-watches.


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Contd..Contd..

The RC mode stands for External RC mode. It is important to note that this is an

_EXTERNAL_ RC mode, ( some PICmicro

devices have an _INTERNAL_ RC mode).

RC mode uses a resistor-capacitor network

connected to the OSC1 pin. When the

device is configured for external RC mode, these

components are automatically driven to producea frequency which will run the PICmicro MCU.


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Contd..Contd..

RC mode is designed for very low-cost

applications. The power consumed will

vary due to the wide range of frequencies

that can be created using this mode


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Contd..Contd..

It is extremely important to note that RC

mode will produce an inaccurate clock

source. In some applications this wont

matter, but applications that are timing

sensitive should not be used with this

mode. For this reason, RC mode is not

recommended for timing sensitive

applications or for RS-232 communication.


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Contd..Contd..

The IntRC mode stands for Internal RC mode

and functions much like the standard External

RC mode.

Unlike External RC mode, in IntRC mode theresistor and capacitor are already provided.

Microcontrollers with this feature have an on-

chip RC oscillator. Current designs run at

approximately 4 MHz.


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Contd..Contd..

IntRC mode is the least expensive

oscillator available since no external

components are needed. It is also useful,

because devices in this mode can oftenuse the OSC1 and OSC2 lines for general

purpose I/O. This feature makes the

PIC12CXXX and other 8-pin PICmicrodevices very popular.


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Contd..Contd..

The ER mode stands for External Resistormode.

ER mode is very similar to External RC mode,

but no capacitor is needed. One resistor controlsthe frequency produced.

Similar to RC mode, ER mode has moderatepower consumption, and is low cost.However,due to the nature of RC oscillators, it is notrecommended for timing sensitive applicationsor for RS-232 use.


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LimitationsLimitations

The PIC architectures have several limitations: Only a single accumulator

A small instruction set

Operations and registers are not orthogonal;some instructions can address RAM and/orimmediate constants, while others can only usethe accumulator

Memory must be directly referenced in arithmeticand logic operations, although indirect

addressing is available via 2 additional registers Register-bank switching is required to access

the entire RAM of many devices


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THANQ !!

Wish you good luck

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