28-08-2012, 03:29 PM
PIC MICRO CONTROLLER
[attachment=32934]
Criteria for choosing a microcontroller
A microcontroller must meet the task at hand efficiency and cost effectively.
Speed. What is highest speed of microcontroller?
To access the data, the address is presented to address pin, the READ pin is activated and after certin time data shows up.
Packaging. Its 40 pin DIP(dual inline package) or QFP(Quad flat package). This is important in terms of space, assembling, prototyping.
Types of microcontrollers
There several dozen types of microcontrollers architectures and venders including
PIC
Intel 8051
Freescale
Rabbit 2000
Ziliog eZ8
Toshiba TLCS-870
And many others types are there. But we will discuss PIC.
Why PIC microcontroller?
As we have discussed criteria for choosing microcontroller.
PIC is very popular in industry.
Wide availability
Extensive collection of application notes.
Availability of low cost or free development tools.
Self-reprogrammable under software control
We will discuss PIC16F877A. Its an 8-bit microcontroller.
PIC16F877A
Peripheral Features
Timer0: 8-bit timer/counter
Timer1: 16-bit timer/counter
Timer2: 8-bit timer/counter
Operating speed: DC – 20 MHz clock input
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
Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI)
Parallel Slave Port (PSP) – 8 bits wide with external RD, WR and CS controls
Analog Features:
10-bit, up to 8-channel Analog-to-Digital Converter (A/D)
Special Microcontroller Features
Self-reprogrammable under software control
In-Circuit Serial Programming™ (ICSP™) via two pins
Single-supply 5V In-Circuit Serial Programming
Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation
Programmable code protection
Power saving Sleep mode
Selectable oscillator options
In-Circuit Debug (ICD) via two pins
Enables you to view variable values, Special Function Register and EEPORM while the program is running.
Analog to Digital Conversion
Important factors are to considered when doing ADC.
Resolution
ADC has n-bit resolution. PIC16F877A supports 8 and 10 bit.
Higher resolution ADC provides smaller step size.
Step size is smallest change that ADC can detect.
Step size can be control with Vref.
Conversion Time
Conversion time is time it takes the ADC to convert the analog input to Digital.
Vref
Vref is input voltage used for reference. Vref and resolution dictates the step size.
For 8-bit step size =Vref/256.
Digital Data Output
Dout=Vin/Step size
ADC channel
Many data acquisition application need more than one ADC. PIC16F877A supports 10 ADC channels.
Start Conversion (SC) and End of Conversion Signals (EOC)
For multiple channels, these is a single digital output register.
SC and EOC is necessary.
When SC is activated, ADC start converting and after conversion data is put in output register.
[attachment=32934]
Criteria for choosing a microcontroller
A microcontroller must meet the task at hand efficiency and cost effectively.
Speed. What is highest speed of microcontroller?
To access the data, the address is presented to address pin, the READ pin is activated and after certin time data shows up.
Packaging. Its 40 pin DIP(dual inline package) or QFP(Quad flat package). This is important in terms of space, assembling, prototyping.
Types of microcontrollers
There several dozen types of microcontrollers architectures and venders including
PIC
Intel 8051
Freescale
Rabbit 2000
Ziliog eZ8
Toshiba TLCS-870
And many others types are there. But we will discuss PIC.
Why PIC microcontroller?
As we have discussed criteria for choosing microcontroller.
PIC is very popular in industry.
Wide availability
Extensive collection of application notes.
Availability of low cost or free development tools.
Self-reprogrammable under software control
We will discuss PIC16F877A. Its an 8-bit microcontroller.
PIC16F877A
Peripheral Features
Timer0: 8-bit timer/counter
Timer1: 16-bit timer/counter
Timer2: 8-bit timer/counter
Operating speed: DC – 20 MHz clock input
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
Universal Synchronous Asynchronous Receiver Transmitter (USART/SCI)
Parallel Slave Port (PSP) – 8 bits wide with external RD, WR and CS controls
Analog Features:
10-bit, up to 8-channel Analog-to-Digital Converter (A/D)
Special Microcontroller Features
Self-reprogrammable under software control
In-Circuit Serial Programming™ (ICSP™) via two pins
Single-supply 5V In-Circuit Serial Programming
Watchdog Timer (WDT) with its own on-chip RC oscillator for reliable operation
Programmable code protection
Power saving Sleep mode
Selectable oscillator options
In-Circuit Debug (ICD) via two pins
Enables you to view variable values, Special Function Register and EEPORM while the program is running.
Analog to Digital Conversion
Important factors are to considered when doing ADC.
Resolution
ADC has n-bit resolution. PIC16F877A supports 8 and 10 bit.
Higher resolution ADC provides smaller step size.
Step size is smallest change that ADC can detect.
Step size can be control with Vref.
Conversion Time
Conversion time is time it takes the ADC to convert the analog input to Digital.
Vref
Vref is input voltage used for reference. Vref and resolution dictates the step size.
For 8-bit step size =Vref/256.
Digital Data Output
Dout=Vin/Step size
ADC channel
Many data acquisition application need more than one ADC. PIC16F877A supports 10 ADC channels.
Start Conversion (SC) and End of Conversion Signals (EOC)
For multiple channels, these is a single digital output register.
SC and EOC is necessary.
When SC is activated, ADC start converting and after conversion data is put in output register.