PIC16F877A Pinout and Pin Configuration Guide

Table of Content
1. PIC16F877A Pinout Diagram and Overview
2. Detailed PIC16F877A Pin Configuration and Description
3. PIC16F877A ICSP Schematic for Programming
4. PIC16F877A Ports and I/O Configuration
5. PIC16F877A Block Diagram and Architecture
6. PIC16F877A Package Dimension - PDIP-40
7. PIC16F877A Pinout FAQs and Tips

1. PIC16F877A Pinout Diagram and Overview

The PIC16F877A is a versatile 8-bit microcontroller from Microchip Technology, renowned for its robust feature set and flexibility in embedded applications. This section provides a clear, detailed pinout diagram of the PIC16F877A, highlighting its 40-pin PDIP configuration and key functionalities. Each pin’s purpose—ranging from power, ground, and oscillator inputs to I/O ports, timers, and communication interfaces (UART, SPI, I²C)—is concisely explained to streamline your design process. Whether you’re prototyping or developing production-grade systems, this overview equips you with essential insights to harness the PIC16F877A’s capabilities efficiently. Explore the diagram and specifications to optimize your next project.

PIC16F877A Pinout Diagram(PDIP-40) Download pdf - P3/P234

2. Detailed PIC16F877A Pin Configuration and Description

Table content excerpted from the PIC16F877A Microchip pdf file Download pdf - 2.5MB/234 pages
Legend: I = input; O = output; I/O = input/output; P = power; — = Not used; TTL = TTL input; ST = Schmitt Trigger input
Note 1: This buffer is a Schmitt Trigger input when configured as the external interrupt.
Note 2: This buffer is a Schmitt Trigger input when used in Serial Programming mode.
Note 3: This buffer is a Schmitt Trigger input when configured in RC Oscillator mode and a CMOS input otherwise.

3. PIC16F877A ICSP Schematic for Programming

PIC16F87XA microcontrollers can be serially programmed while in the end application circuit. This is simply done with two lines for clock and data and three other lines for power, ground and the programming voltage. This allows customers to manufacture boards with unprogrammed devices and then program the microcontroller just before shipping the product. This also allows the most recent firmware or a custom firmware to be programmed. When using ICSP, the part must be supplied at 4.5V to 5.5V if a bulk erase will be executed. This includes reprogramming of the code-protect, both from an on state to an off state. For all other cases of ICSP, the part may be programmed at the normal operating voltages. This means calibration values, unique user IDs or user code can be reprogrammed or added.

Low-Voltage (Single-Supply)  ICSP Programming

The LVP bit of the configuration word enables lowvoltage ICSP programming. This mode allows the microcontroller to be programmed via ICSP using a VDD source in the operating voltage range. This only means that VPP does not have to be brought to VIHH but can instead be left at the normal operating voltage. In this mode, the RB3/PGM pin is dedicated to the programming function and ceases to be a general purpose I/O pin. During programming, VDD is applied to the MCLR pin. To enter Programming mode, VDD must be applied to the RB3/PGM provided the LVP bit is set. The LVP bit defaults to on (‘1’) from the factory. If Low-Voltage Programming mode is not used, the LVP bit can be programmed to a ‘0’ and RB3/PGM becomes a digital I/O pin. However, the LVP bit may only be programmed when programming is entered with VIHH on MCLR. The LVP bit can only be charged when using high voltage on MCLR. It should be noted, that once the LVP bit is programmed to ‘0’, only the High-Voltage Programming mode is available and only High-Voltage Programming mode can be used to program the device. When using low-voltage ICSP, the part must be supplied at 4.5V to 5.5V if a bulk erase will be executed. This includes reprogramming of the code-protect bits from an on state to an off state. For all other cases of low-voltage ICSP, the part may be programmed at the normal operating voltage. This means calibration values, unique user IDs or user code can be reprogrammed or added.

Download pdf - 180KB/22 pages

4. PIC16F877A Ports and I/O Configuration

The PIC16F877A microcontroller features 33 GPIO pins organized into five bidirectional I/O ports (PORTA to PORTE), providing flexible interfacing for embedded systems. Each port is controlled by corresponding TRISx and PORTx registers, enabling precise pin configuration and data manipulation. Below is a concise overview tailored for electronic engineers:

• PORTA (6 pins, RA0–RA5): A versatile port with analog capabilities (AN0–AN4). Configure as digital I/O by setting ADCON1 to 0x06. TRISA sets pin direction (1 = input, 0 = output). RA4 is an open-drain output, requiring an external pull-up resistor (e.g., 4.7kΩ).
• PORTB (8 pins, RB0–RB7): Digital I/O with interrupt-on-change and weak pull-up options. TRISB controls direction. Ideal for external interrupts (RB0/INT) and serial communication (e.g., RB6/RB7 for ICSP).
• PORTC (8 pins, RC0–RC7): Digital I/O with peripherals like UART (RC6/TX, RC7/RX) and PWM (RC1/CCP2, RC2/CCP1). TRISC sets direction. Peripherals may override TRIS settings, so consult the datasheet for conflicts.
• PORTD (8 pins, RD0–RD7): Digital I/O with parallel slave port capability. TRISD configures direction. Suitable for high-current applications due to robust drive strength.
• PORTE (3 pins, RE0–RE2): Bidirectional I/O with analog inputs (AN5–AN7). TRISE sets direction, except for RE3 (input-only). Commonly used for parallel slave port control.

Key Configuration Notes:

• TRISx Registers: Set to 1 for input, 0 for output. Use bit-level operations to avoid read-modify-write issues (e.g., BSF, BCF in assembly or TRISBbits.TRISB0 = 0 in C).
• PORTx Registers: Read input states or write output values. Writing 1 sets a pin high; 0 sets it low.
• Multiplexed Functions: Many pins support alternate functions (e.g., ADC, SPI, I²C). Disable peripherals via control registers (e.g., SPEN, ADCON0) to use pins as general-purpose I/O.
• Electrical Specs: Operate within 2.0V–5.5V. Check Section 17.0 (Electrical Characteristics) in the datasheet( Download pdf - 2.5MB/234 pages ) for current limits and timing.

This configuration flexibility makes the PIC16F877A ideal for applications like sensor interfacing, motor control, and communication systems. For detailed register settings and example code, refer to the PIC16F877A datasheet or MPLAB XC8 tutorials.

5. PIC16F877A Block Diagram and Architecture

PIC16F877A Block Diagram Download pdf - P6/P234

The PIC16F877A, an 8-bit microcontroller from Microchip Technology, is built on a Harvard architecture with a robust feature set for embedded applications. This section provides a concise overview of its block diagram and internal architecture, tailored for electronic engineers designing efficient systems.

• Core Architecture:

  • 8-bit CPU: Executes instructions in a single cycle (4 oscillator clocks), except for branches. Operates at up to 20 MHz with a 200 ns instruction cycle.
  • Program Memory: 8K x 14-bit Flash, supporting up to 8,192 instructions. Erasable and programmable via ICSP.
  • Data Memory: 368 bytes of RAM and 256 bytes of EEPROM for flexible data storage.
  • Stack: 8-level deep hardware stack for subroutine calls and interrupts.
    
    

• Key Functional Blocks:

  • Oscillator Module: Supports multiple modes (XT, HS, LP, RC) with external crystals or clocks. Configured via OSCCON for precise timing.
  • I/O Ports: 33 GPIO pins across five ports (A–E), configurable via TRISx and PORTx registers. Ports support analog inputs, PWM, and communication peripherals.
  • Timer Modules: Three timers (Timer0, Timer1, Timer2) for timekeeping, PWM generation, and event counting. Timer1 supports external clock inputs.
  • Communication Interfaces: Includes USART (for serial communication), MSSP (SPI/I²C), and parallel slave port for versatile data exchange.
  • Analog Features: 10-bit ADC with 8 channels (AN0–AN7) for precise analog-to-digital conversion, configured via ADCON0/1.
  • Interrupt Controller: Supports multiple interrupt sources (e.g., timers, external pins, ADC) with priority handling for real-time responsiveness.
    
    

• Block Diagram Highlights:

  • The block diagram illustrates the separation of program memory and data memory buses, characteristic of Harvard architecture, ensuring simultaneous instruction fetch and data access.
  • Peripheral modules (e.g., ADC, USART, timers) connect to the CPU via a shared data bus, controlled by special function registers (SFRs).
  • Power management features, including sleep mode and brown-out reset, optimize energy efficiency.

Design Considerations:

• Configure peripherals via SFRs (e.g., TXSTA for USART, T2CON for Timer2) to avoid conflicts with GPIO functions.
• Use MPLAB XC8 or assembly for efficient code, leveraging the 35-instruction set for compact programming.
• Refer to Section 2.0 (Device Overview) and Section 3.0 (Oscillator Configurations) in the PIC16F877A datasheet Download pdf - 2.5MB/234 pages for detailed block diagram and setup guidance.

The PIC16F877A’s architecture balances performance and flexibility, making it ideal for applications like industrial control, sensor networks, and IoT devices. Explore the block diagram and register settings to optimize your design.

6. PIC16F877A Package Dimension - PDIP-40

PIC16F877A Case Package Dimension(PDIP-40)

PIC16F877A Package Dimension(PDIP-40) Download pdf - P211/P234

Note:
1). * Controlling Parameter; 2). § Significant Characteristic; 3). Dimensions D and E1 do not include mold flash or protrusions. Mold flash or protrusions shall not exceed .010” (0.254mm) per side.

7. PIC16F877A Pinout FAQs and Tips

The PIC16F877A, a 40-pin 8-bit microcontroller from Microchip Technology, offers versatile pinout configurations for embedded designs. This section addresses common questions and provides practical tips for electronic engineers to optimize pin usage and avoid pitfalls.

FAQs:

Q: What are the power and ground pins?  

A: VDD (pins 11, 32) and VSS (pins 12, 31) support 2.0V–5.5V operation. Use 0.1µF decoupling capacitors near each VDD pin to ensure stability.

Q: How is the MCLR pin configured?  

A: MCLR (pin 1) is the master clear reset. Connect a 4.7kΩ–10kΩ pull-up resistor to VDD and an optional 0.1µF capacitor to ground for noise immunity. Set CONFIG bits to enable/disable reset functionality.

Q: Which pins support analog inputs?  

A: PORTA (RA0–RA5) and PORTE (RE0–RE2) provide 8 ADC channels (AN0–AN7). Disable analog functions via ADCON1 (e.g., 0x06 for all digital) to use as digital I/O.

Q: Can I use RB6/RB7 for general I/O during ICSP?  

A: RB6 (PGC) and RB7 (PGD) are used for ICSP. Avoid loading these pins during programming to prevent signal interference. Post-programming, they can function as general I/O.

Q: What is the role of the RB3/PGM pin in low-voltage programming?  

A: When the LVP bit is enabled (‘1’ in CONFIG word), RB3 is dedicated to low-voltage ICSP and cannot be used as I/O. Disable LVP (set to ‘0’) to reclaim RB3 as a digital I/O pin, but this requires high-voltage programming thereafter.

Practical Tips:

• Pin Multiplexing: Many pins support alternate functions (e.g., USART on RC6/RC7, PWM on RC1/RC2). Check SFRs (e.g., SPEN, CCP1CON) to disable peripherals and free pins for general I/O.
• Open-Drain Pins: RA4 and RB3 (if LVP disabled) are open-drain outputs. Use external pull-up resistors (e.g., 4.7kΩ) for reliable logic-high signals.
• Current Limits: Source/sink up to 25mA per pin, with a 200mA total limit per port. Refer to Section 17.0 (Electrical Characteristics) in the datasheet for detailed specs.
• ICSP Setup: For in-circuit programming, isolate RB6/RB7 from heavy loads (e.g., via resistors or buffers) to ensure reliable clock and data signals.
• Debugging Tip: If a pin behaves unexpectedly, verify TRISx settings (1 = input, 0 = output) and ensure no peripheral overrides (e.g., ADC, SPI) are active.

Resources: Consult Section 2.0 (Device Overview) and Section 14.0 (In-Circuit Serial Programming) in the PIC16F877A datasheet for pinout diagrams and ICSP details. Use MPLAB X IDE with XC8 compiler for configuration examples.
These FAQs and tips streamline your design process, ensuring robust pin configuration for applications like sensor interfacing, motor control, and communication systems.