Introduction to PIC Microcontroller: Architecture, Features, and Applications

Catalog

Ⅰ Introduction

The word PIC stands for Peripheral Interface Controller. This was originally designed to help PDP computers monitor their peripheral devices, and is thus referred to as a peripheral interface unit. Compared to other microcontrollers, these microcontrollers can run a program very quickly and comfortably. The architecture of PIC Microcontrollers is based on Harvard architecture. Due to their ease of programming, limited availability, easy to integrate with other peripherals, low cost, wide user base, and serial programming capacity (reprogramming with flash memory), etc., PIC microcontrollers are quite common.

PIC Microcontroller

Each architecture of the PIC microcontroller consists of certain registers and stacks where registers act as Random Access Memory (RAM) and the return addresses are saved by the stack. RAM, flash memory, timers/counters, EEPROM, I/O ports, USART, CCP (Capture/Compare/PWM module), SSP, Comparator, ADC (analog to digital converter), PSP(parallel slave port), LCD and ICSP are the key features of PIC microcontrollers (in circuit serial programming). Based on the internal architecture, the 8-bit PIC microcontroller is categorized into four groups, such as Base Line PIC, Mid Range PIC, Enhanced Mid Range PIC, and PIC18.

The evolution of PIC microcontrollers has produced multiple generations with progressively enhanced features, while maintaining backward compatibility that preserves developers' investments in code and knowledge (Huang, 2018). This strategic approach to product development has contributed significantly to the enduring popularity of PIC microcontrollers among hobbyists, educators, and professional embedded systems designers.

Ⅱ Architecture

The architecture of the PIC microcontroller includes the CPU, I/O ports, memory organization, A/D converter, timers/counters, interrupts, serial communication, oscillator, and CCP module, which are discussed in depth below.

8051 MicroController Architecture

1.CPU

It is not distinct from other CPU microcontrollers and consists of the ALU, CU, MU and accumulator, etc., of the PIC microcontroller CPU. The logic unit of arithmetic is primarily used for arithmetic operations and for making logical decisions. Memory is used during processing for storing the instructions. Control units that are attached to the CPU are used to control the internal and external peripherals and the accumulator is used to store the effects and further operations.

2.Random Access Memory (RAM)

These registers, as the name suggests, are only used for general purposes. For instance, when using the PIC microcontroller, we want to multiply two numbers. Generally, to multiply and store the numbers in other registers, we use registers. The Processor can quickly access the data in the registers, so these registers do not have any special features.

3.Special Function Registers

As the term SFR suggests, these registers are used for special purposes only. These registers can operate according to the functions delegated to them and will not be used as ordinary registers. For example, if the STATUS register can not be used to store the data, these registers are used to represent the program's function or status. Thus, the SFR feature can not be changed by the user; the function is supported by the retailer at the time of development.

4.Read Only Memory (ROM)

Memory Read Only is a secure memory that is used to indefinitely store records. The architecture ROM holds the instructions or applications in the PIC microcontroller architecture, according to the application the microcontroller runs. The ROM is also called application memory, where the user writes the microcontroller program and stores it indefinitely, and the CPU eventually executes the program. The efficiency of the microcontrollers depends on the instructions that the CPU executes.

5.Electrically Erasable Programmable Read Only Memory (EEPROM)

We can only write the software in the usual ROM until we can't use the microcontroller several times again. But, we can program the ROM several times in the EEPROM.

6.Flash Memory

Flash memory is also programmable read-only memory (PROM) of which thousands of times we can read, write and delete the program. The PIC microcontroller typically uses this ROM form.

7.Stack

When an interrupt happens, the interrupt and the current process address must be executed first by the PIC microcontroller. This is then stored in the stack that is being executed. Upon completion of the interrupt execution, the microcontroller calls the process with the aid of the address that is stored in the stack and the process is executed.

8.I/O Ports

Five ports, such as Port A, Port B, Port C, Port D & Port E, make up the PIC16 series.

Port A is a 16-bit port that, depending on the TRISA (Tradoc Intelligence Support Activity) register status, can be used as an input or output port.

Port B is an 8-bit port that can be used as an input port as well as an output port.

Port C is 8-bit and the state of the TRISC register specifies the input of the output operation.

Port D is an 8-bit port that serves as a slave port for microprocessor BUS connections.

Port E is a 3-bit port serving the additional purpose of analog to digital converter control signals.

9.BUS

The BUS is used to transfer data from one peripheral to another to receive it. It is categorized into two categories, such as bus and address data.

PIC Microcontroller bus

Data Bus: It is used for sending or receiving data only.

Address Bus: To relay the memory address from the peripherals to the CPU, the address bus is used. I/O pins are used to connect external peripherals; both UART and USART are serial networking protocols used to connect serial devices such as GSM, GPS, Bluetooth, IR, etc.

10.A/D converters

This analog to digital converter's key objective is to transform analog voltage values to digital voltage values. The PIC microcontroller A/D package consists of 5 28-pin device inputs and 8 40-pin device inputs. ADCON0 and ADCON1 special registers control the operation of an analog to digital converter. The upper bits of the converter are stored in the ADRESH register, and the lower bits are stored in the ADRESL register. It needs 5V of an analog reference voltage for this operation.

11.Timers/ Counters

There are four timers/counters in the PIC microcontroller where one 8-bit timer and the other timers have the ability to choose 8 or 16-bit mode. For example, timers are used to create precise behavior, generating unique time delays between two operations.

12.Interrupts

The PIC microcontroller consists of 20 internal interrupts and three external sources of interrupts connected to various peripherals such as ADC, USART, Timers, etc.

13.Serial Communication

The method of transmitting data one bit at a time sequentially over a transmission medium is serial communication.

USART: The USART name stands for Universal Synchronous and Asynchronous Receiver and Transmitter, which is a two-protocol serial contact. It is used with reference to clock pulses to send and receive the data bit by bit over a single cable. There are two TXD and RXD pins on the PIC microcontroller. To send and receive the data serially, these pins are used.

SPI Protocol: Serial Peripheral Interface stands for the word SPI. This protocol is used to transfer data to other peripherals, such as SD cards, sensors, and shift registers, between the PIC microcontroller. On a standard clock source, PIC microcontrollers allow three wire SPI communications between two machines. The SPI protocol data rate is greater than that of USART.

I2C Protocol: The term I2C stands for Inter-Integrated Circuit and is a serial protocol used to connect low-speed devices such as EEPROMS, microcontrollers, A/D converters, etc. Two-wire interface or I2C connectivity between two devices that can act as both Master and Slave devices is enabled by the PIC microcontroller.

14.Oscillators

Oscillators are used for producing timing. External oscillators such as RC oscillators or crystal oscillators are part of the Pic microcontroller. The crystal oscillator is connected between the two pins of the oscillator. Each pin that determines the mode of the oscillator operation is attached to the value of the capacitor. Crystal mode, a high-speed mode, and the low-power mode are the settings. For RC oscillators, the clock frequency is calculated by the resistor & capacitor value and the clock frequency range is 30KHz to 4MHz.

15.CCP module

The CCP module name stands for capture/compare/PWM where three modes are used, such as capture mode, compare mode and PWM mode.

Capture Mode: Capture mode captures the moment of the signal's arrival, or in other words, the value of the Timer1 is recorded when the CCP pin goes high.

Mode Compare: Mode Compare functions as an analog comparator. When a certain reference value is met by the timer1 value, it produces an output.

PWM Mode: PWM mode offers a 10-bit resolution and programmable service cycle modulated display with pulse frequency.

Ⅲ Advantages and disadvantages

PIC Microcontroller Advantages:

PIC microcontrollers are compatible and the number of PIC defects is very limited. The PIC microcontroller's efficiency is very fast due to the use of the RISC architecture.

Power consumption is very low as compared to other microcontrollers, and programming is also very simple.

Interfacing an analog computer without any additional circuitry is easy.

PIC Microcontroller disadvantages:

Due to the use of RISC architecture, the program length is long (35 instructions)

There is a single accumulator and program memory is not available.

Ⅳ PIC Microcontroller Families

The 8-bit PIC microcontroller lineup is categorized into four primary families, each with distinctive characteristics:

1. Baseline PIC (PIC10, PIC12, PIC16)

These entry-level microcontrollers feature a 12-bit instruction word length and limited peripheral sets. They typically offer modest program memory (up to a few kilobytes), minimal RAM, and basic peripherals. Despite their limitations, they excel in simple applications where cost and power consumption are critical factors (Smith, 2019).

2. Mid-Range PIC (PIC16)

Mid-range PICs utilize a 14-bit instruction word length and incorporate enhanced peripheral sets. They typically offer larger memory capacities, improved interrupt handling, and additional peripherals compared to baseline models. This family represents a balanced compromise between capability and cost, making it suitable for a wide range of moderate-complexity applications (Reese et al., 2022).

3. Enhanced Mid-Range PIC (PIC12, PIC16)

Enhanced mid-range PICs maintain the 14-bit instruction word length but introduce significant architectural improvements, including:

Expanded instruction set

Enhanced interrupt handling

Improved peripheral functionality

More efficient memory addressing

Reduced power consumption

These enhancements deliver performance improvements while maintaining compatibility with standard mid-range devices (Ibrahim, 2021).

4. PIC18

The PIC18 family represents the high-end of 8-bit PIC microcontrollers, featuring a 16-bit instruction word length and advanced capabilities:

Expanded memory addressing

Enhanced instruction set with optimizations for C language compilation

Advanced peripheral integration

Superior performance metrics

Extended operating temperature ranges

This family addresses complex applications requiring substantial processing power while remaining within the 8-bit microcontroller category (Gardner, 2020).

V Applications

PIC microcontrollers find application across diverse industries and products:

• Consumer Electronics: Remote controls, small appliances, toys, and gadgets

• Automotive Systems: Engine control units, dashboard instrumentation, and comfort control systems

• Industrial Control: Machine control, process monitoring, and automation systems

• Medical Devices: Patient monitoring equipment, infusion pumps, and diagnostic tools

• Security Systems: Alarm panels, access control, and surveillance equipment

• Communication Devices: Modems, routers, and network interfaces

• Educational Platforms: Teaching microcontroller concepts and embedded programming principles (Wilmshurst, 2022)

VI Conclusion

We recognize that the microcontroller is an embedded chip consisting of CPUs, RAM, ROMs, timers, counters, etc. Similarly, the architecture of the PIC microcontroller consists of RAM, ROM, CPU, clocks, counters, and supports protocols such as SPI, CAN, and UART to communicate with other peripherals. Thanks to the low power consumption, high processing capacity, and convenient availability of its supporting hardware and software resources such as compilers, debuggers, and simulators, PIC microcontrollers are currently commonly used for industrial purposes.

References

Gardner, N. (2020). Microcontroller programming and interfacing with PIC18F (3rd ed.). Morgan & Claypool Publishers. 

Huang, H. W. (2018). PIC microcontroller: An introduction to software and hardware interfacing (3rd ed.). Cengage Learning.

Ibrahim, D. (2021). Advanced PIC microcontroller projects in C: From USB to RTOS with the PIC18F series (2nd ed.). Newnes. 

Mazidi, M. A., McKinlay, R. D., & Causey, D. (2021). PIC microcontroller and embedded systems: Using assembly and C for PIC18 (2nd ed.). Pearson Education.

Peatman, J. B. (2019). Design with PIC microcontrollers (3rd ed.). Pearson Education.

Reese, R. B., Bruce, J. W., & Jones, B. A. (2022). Microcontrollers: From assembly language to C using the PIC18Fxx2 (2nd ed.). Charles River Media.

Smith, D. W. (2019). PIC in practice: A project-based approach (3rd ed.). Newnes. 

Verle, M. (2020). PIC microcontrollers: Programming in C (2nd ed.). mikroElektronika.

Wilmshurst, T. (2022). Designing embedded systems with PIC microcontrollers: Principles and applications (3rd ed.). Newnes.