What is a PIC Microcontroller: The Harvard Architecture

January 28, 2020 Cadence PCB Solutions

PIC Microcontroller on a green printed circuit board

 

It sounds cliche but embedded system designers had it easier today than when I started my first microcontroller-based project. Back then, I was using an EPROM-based microcontroller with an expensive programming tool, and development software. When microcontrollers are adopting the flash technology, I had my first taste of PIC microcontrollers.

Back then, PIC microcontrollers were probably lesser known than some of its competitors, but its free development software and cheap programming tool makes it an attractive option. I was hooked to PIC from the start, and I am still a fan today of its range of microcontrollers.

What is a PIC Microcontroller

Today, you ought to have heard of the PIC microcontroller, particularly if you’re an embedded system engineer or a PCB designer. It’s the popular line of microcontroller that is currently manufactured by Microchip Technology Inc. 

The PIC microcontroller was introduced in 1993 by Microchip although the original chip design was created by General Instruments in 1985. PIC microcontrollers are meant to enable simple programming and interfacing in embedded system design. Most of the PIC microcontrollers that hit the market are 8-bits microcontrollers, although Microchip did introduce some 16-bits and 32-bits PIC microcontrollers.

 

Harvard architecture of programmable logic for PIC microcontrollers

The Harvard Architecture used by PIC Microcontrollers.

 

PIC microcontrollers are based on the Harvard architecture where program and data busses are kept separate. Early versions of PIC microcontrollers use EPROM to store the program instruction but have adopted the flash memory since 2002 to allow better erasing and storing of the code.

Thanks to its simplicity in architecture and ease-of-use, PIC microcontrollers have proved to be a hit amongst hobbyists, students, and professionals. The PIC16F84 and PIC16F877 were some of the most popular PIC microcontrollers with basic functionalities. Applications that require richer peripherals, higher performance or memory can rely on the PIC18F family. 

PIC Microcontroller Features

One of the reasons why I’m such a big fan of PIC microcontrollers is that they often have similar features. This makes working with various part numbers of PIC microcontrollers easy as the architecture, peripherals, and design cycle are almost the same. 

Basic PIC microcontrollers may have limited peripherals while their more advanced counterparts are rich with communications, memory, I/Os, and special function peripherals. However, you can expect the PIC microcontrollers generally have these features.

Memory

Modern PIC microcontrollers are built with Flash memory to store program instructions. Flash memory has a larger capacity and is easily-erased compared to EPROM or OTP microcontrollers. 

PIC microcontrollers also feature built-in RAM and EEPROM that are useful in storing application parameters and run-time variables. 

You’ll also find that the special function registers and stack pointers of the PIC microcontrollers are quite standard across various part numbers.

Oscillator

Like other microcontrollers, PIC needs a clocking source to drive its system timing. This is often done with a crystal or in some PICs, an internal oscillator

I/O

PIC microcontrollers labeled segregate I/O pins by ports (e.g. PORTA, PORTB). For an 8-bit PIC, a single port contains 8 individual pins. Each pin can be configured as input, output or alternative peripheral functions.

Peripherals

In most PIC microcontrollers, you’ll also find the following peripherals. 

  • EUSART - provides serial UART communication. 

  • SSP - allows SPI and I2C interface.

  • CCP - capture and compare module and PWM output.

  • ADC - convernts analog siginal to digital values.

  • Timers - Depending on the part number, there could be several timers in the PIC.

Designing With A PIC Microcontroller

It is fair to suggest that Microchip’s dominant market share is due to its comprehensive development support that reduces development cost. For example, the MPLAB IDE, which is used to create program code for PIC microcontrollers, has always been downloadable for free. Programming tools, such as the PICKIT, are more affordable compared to other manufacturers.

 

PIC microcontroller on a device plugged in for testing timing

PIC microcontrollers are popular amongst hobbyists.

 

PIC microcontrollers have proved to be popular amongst hobbyists with their affordability and ease-of-use. With that said, PIC microcontrollers are also viable solutions for commercial and industrial applications. It is easy to kickstart a PCB project with the PIC. 

PCB designers could bank on its rich knowledgebase where datasheets, user guides, and various application notes are available. In recent years, various startup kits with popular PIC microcontrollers are made available. With the right PCB design software, you’ll also have access to readily-available libraries of PIC microcontrollers. OrCAD can provide you with the collaborative layout and design tool that you need to get any device made easily and with the utmost care. 

If you’re looking to learn more about how Cadence has the solution for you, talk to us and our team of experts.

About the Author

Cadence PCB solutions is a complete front to back design tool to enable fast and efficient product creation. Cadence enables users accurately shorten design cycles to hand off to manufacturing through modern, IPC-2581 industry standard.

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