PIC Microcontrollers

PIC Microcontrollers
16th May 2009 No Comments Uncategorised admin

The PIC Microcontroller Family

 

The PIC microcontroller family is manufactured by Microchip Technology Inc. Currently

they are one of the most popular microcontrollers, used in many commercial and industrial

applications. Over 120 million devices are sold each year.

The PIC microcontroller architecture is based on a modified Harvard RISC (Reduced Instruction

Set Computer) instruction set with dual-bus architecture, providing fast and fl exible design

with an easy migration path from only 6 pins to 80 pins, and from 384 bytes to 128 kbytes of

program memory.

PIC microcontrollers are available with many different specifi cations depending on:

 

• Memory Type

– Flash

– OTP (One-time-programmable) …… READ MORE

The PIC Microcontroller Family

 

The PIC microcontroller family is manufactured by Microchip Technology Inc. Currently

they are one of the most popular microcontrollers, used in many commercial and industrial

applications. Over 120 million devices are sold each year.

The PIC microcontroller architecture is based on a modified Harvard RISC (Reduced Instruction

Set Computer) instruction set with dual-bus architecture, providing fast and fl exible design

with an easy migration path from only 6 pins to 80 pins, and from 384 bytes to 128 kbytes of

program memory.

PIC microcontrollers are available with many different specifi cations depending on:

 

• Memory Type

– Flash

– OTP (One-time-programmable)

– ROM (Read-only-memory)

– ROMless

• Input–Output (I/O) Pin Count

– 4–18 pins

– 20–28 pins

– 32–44 pins

– 45 and above pins

• Memory Size

– 0.5–1 K

– 2–4 K

– 8–16 K

– 24–32 K

– 48–64 K

– 96–128 K

• Special Features

– CAN

– USB

– LCD

– Motor Control

– Radio Frequency

 

Although there are many models of PIC microcontrollers, the nice thing is that they are

upward compatible with each other and a program developed for one model can very easily, in

many cases with no modifi cations, be run on other models of the family. The basic assembler

instruction set of PIC microcontrollers consists of only 33 instructions and most of the family

members (except the newly developed devices) use the same instruction set. This is why a

program developed for one model can run on another model with similar architecture without

any changes.

 

All PIC microcontrollers offer the following features:

• RISC instruction set with only a handful of instructions to learn

• Digital I/O ports

• On-chip timer with 8-bit prescaler

• Power-on reset

• Watchdog timer

• Power-saving SLEEP mode

• High source and sink current

• Direct, indirect, and relative addressing modes

• External clock interface

• RAM data memory

• EPROM or Flash program memory

Some devices offer the following additional features:

• Analog input channels

• Analog comparators

• Additional timer circuits

• EEPROM data memory

• External and internal interrupts

• Internal oscillator

• Pulse-width modulated (PWM) output

• USART serial interface

 

Some even more complex devices in the family offer the following additional features:

• CAN bus interface

• I2C bus interface

• SPI bus interface

• Direct LCD interface

• USB interface

• Motor control

 

Although there are several hundred models of PIC microcontrollers, choosing a microcontroller

for an application is not a diffi cult task and requires taking into account these factors:

 

• Number of I/O pins required

• Required peripherals (e.g., USART, USB)

• The minimum size of program memory

• The minimum size of RAM

• Whether or not EEPROM nonvolatile data memory is required

• Speed

• Physical size

• Cost

 

The important point to remember is that there could be many models that satisfy all of

these requirements. You should always try to fi nd the model that satisfi es your minimum

requirements and the one that does not offer more than you may need. For example, if you

require a microcontroller with only 8 I/O pins and if there are two identical microcontrollers,

one with 8 and the other one with 16 I/O pins, you should select the one with 8 I/O pins.

Although there are several hundred models of PIC microcontrollers, the family can be broken

down into three main groups, which are:

• 12-bit instruction word (e.g., 12C5XX, 16C5X) (also called as the 12

Series and the 16C5X Series)

• 14-bit instruction word (e.g., 16F8X, 16F87X) (also referred as the

16 Series)

• 16-bit instruction word (e.g., 17C7XX, 18C2XX) (also referred as the

17 Series and the 18 Series).

 

All three groups share the same RISC architecture and the same instruction set, with a few

additional instructions available for the 14-bit models, and many more instructions available

for the 16-bit models. Instructions occupy only one word in memory, thus increasing the code

effi ciency and reducing the required program memory. Instructions and data are transferred on

separate buses, so the overall system performance is increased.

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