PIC16F877A I/O PORTs PROGRAMMING

I/O PORT PROGRAMMING IN PIC16F877A

•  PIC 116F877A has 40 pins, 33 pins are set as 5 Input/Output ports: PORTA, PORTB, PORTC, PORTD and PORTE.
•  PORTA has 6 pins, PORTB/PORTC/PORTD has 8 bins while PORTE has 3 pins.
•   Each port of PIC16F877A has some others functions, such as ADC, Interrupts, Timers, Serial Communication…
•  Each port can be configured as input or output by setting to its corresponding TRIS register.
• In this article, I will talk about PIC16F877A Digital I/O function first.

PORT AND TRIS REGISTER

•  The data direction is depended on TRIS register. Each Port has its corresponding TRIS, i.e: PORTA & TRISA, PORTB & TRISB… 
• Setting an TRIS bit to logic 1 will make the corresponding PORT pin an Input.
• Setting a TRIS bit to logic 0 will make the corresponding  PORT pin an Output.
•    Reading the PORT register reads the status of that PORT (pins), whereas writing to it will write to the port latch.

EXAMPLE TO OBSERVE THE STATUS OF OUTPUT PORT.

•      In this example, we will build a simple circuit to test the output function of PIC16F877A’s PORT. Please refer the following schematic:

•      Now we set RB0 as an output, then send the logic 1 to turn on the LED and toggle it after every 500ms. The code below is writing in C language. After compiled, we send the Hex file to PIC via ICSP port (by any programmer you have).

• Turn on/off the LEDs after 500ms:

• LED "running" effect:

• Let's combine 3 programs above into one and see the result:

For detail description about PIC16F877A’s PORT & TRIS registers, please refer to its datasheet from Microchip webpage:

In next articles, we will practice about I/O programming by building more LED flashing programs with PIC MCU and push button..