PIC 16F877A Basics

PIC 16F877A Basics

PIC 16F877A is a 40pin IC with 20MHz clock speed with 200ns instruction cycle. It has only 35 instructions set and comes under RISC architecture.

Memory:

• Up to 8K x 14 words of Flash Program Memory.
•  Up to 368 x 8 bytes of Data Memory (RAM).
• Up to 256 x 8 bytes of EEPROM Data Memory.

Peripheral Features:

• 1Timers: Timer is a clock that controls the sequence of an event while counting in fixed intervals of time. A Timer is used for producing precise time delay. Secondly, it can be used to repeat or initiate an action after/at a known period of time. This feature is very commonly used in several applications. An example could be setting up an alarm which triggers at a point of time or after a period of time.

PIC 16F877A consists of 3 timers timer0, timer1 and timer2

 Timer0: 8-bit timer/counter with 8-bit prescaler.

Timer1: 16-bit timer/counter with prescaler.

Timer2: 8-bit timer/counter with 8-bit period.

• 2    PWM: PWM stands for Pulse Width Modulation and is the method to produce variable voltages using digital means. PIC 16F877A has 2 PWM peripherals with maximum resolution 10 bit.

• 3   ADC: An Analog to Digital Converter (ADC) is a very useful feature that converts an analog voltage on a pin to a digital number. By converting from the analog world to the digital world, we can begin to use electronics to interface to the analog world around us.

          PIC 16F877A has 10-bit, 8-channel ADC.

• 4 USART: Universal Synchronous Asynchronous Receiver Transmitter (USART) is used for serial communication. PIC 16F877A has USART receiver transmitter with 9 bit address detection.

• 5    SPI: Serial Peripheral Interface (SPI) is an interface bus commonly used to send data between microcontrollers and small peripherals such as shift registers, sensors, and SD cards. It uses separate clock and data lines, along with a select line to choose the device you wish to talk to.

          PIC 16F877A consists of one SPI with master mode only. 

• 6    I2C: I²C (pronounced I-squared-C) created by Philips Semiconductors and commonly written as 'I2C' stands for Inter-Integrated Circuit and allows communication of data between I2C devices over two wires. It sends information serially using one line for data (SDA) and one for clock (SCL).

          PIC 16F877A has one I2C peripheral with master/slave mode.

• 7   Brown-out Reset (BOR): Brown out is a potentially dangerous state which occurs at the moment the microcontroller is being turned off or when power supply voltage drops to the lowest level due to electric noise. As the microcontroller consists of several circuits which have different operating voltage levels, this can cause its out of control performance. In order to prevent it, the microcontroller usually has a circuit for brown out reset built-in. This circuit immediately resets the whole electronics when the voltage level drops below the lower limit.