"LEDOn" Experiment

This is the first experiment where a PICmicro® MCU is actually programmed and run. This experiment simply waits for a button to be pressed and turns on an LED. The circuit is:

The parts needed for this experiment are listed in the table:

Part Description Required for the YAP-II/EMU-II?

PICmicro® MCU PIC16F84-04/P
PIC16F877-04/P In Socket

Vdd/Vss Decoupling Capacitor 0.1 uF (Any Type) No

_MCLR Pull Up Resistor 10K, 1/4 Watt No

4 MHz Ceramic Resonator Three Leaded Ceramic Resonator with Built in 27-33pF Capacitors No

RA0 Pull Up 10K, 1/4 Watt No - "BUT1" Used

RA0 Push Button Momentary On/Modified for Breadboard No - "BUT1" Used

RB0 LED Current Limiting Resistor 220W, 1/4 Watt No - "LED1" Used

RB0 LED Any Type No - "LED1" Used

Breadboard Any Type No

+5 Volt "Vcc" Power Supply Any Type No

Using a breadboard, the experiment is wired using the guide:

If the EMU-II or YAP-II is used, the experiment is wired as:

The experiment can be modeled as the "C" source application:

main()				//  "LEDOn" Experiment
{

  PORTB.0 = High;			//  Make RB0 High so LED is Off
  TRISB.0 = Output;		//  Make RB0 Output for LED Driving

  while (1 == 1)			//  Loop Forever
    PORTB.0 = PORTA.0;

}  //  end LEDOn

The source code listed below can be accessed from the CD-ROM by clicking Here.

 title  "ledon - Turn on a LED when a Button is Pressed"
;
;  This is the First Program to be Burned in and Run in a PIC.
;
;  The Program simply sets up Bit 0 of Port "A" to Output and then
;   Sets it Low when RA0 is pulled low.
;
;  Hardware Notes:
;   _MCLR is tied through a 4.7K Resistor to Vcc and PWRT is Enabled
;   A 220 Ohm Resistor and LED is attached to PORTB.0 and Vcc
;   A 10K pull up is connected to RA0 and it's state is passed to 
;    RB0
;
;  Myke Predko
;  99.12.03
;
  LIST R=DEC
 ifdef __16F84
  INCLUDE "p16f84.inc"
 else
 ifdef __16F877
  INCLUDE "p16f877.inc"
 endif

;  Registers

 ifdef __16F84
 __CONFIG _CP_OFF & _WDT_OFF & _XT_OSC & _PWRTE_ON
 else
 __CONFIG _CP_OFF & _WDT_OFF & _XT_OSC & _PWRTE_ON & _DEBUG_OFF & _LVP_OFF & _BODEN_OFF
 endif

  PAGE
;  Mainline of ledon

 org     0

  nop					  ;  "nop" is Required for Emulators

  bsf    PORTB, 0               ;  Make the LED on PORTB.0 "off"

  bsf    STATUS, RP0            ;  Goto Bank 1 to set Port Direction
  bcf    TRISB ^ 0x080, 0       ;  Set RB0 to Output
  bcf    STATUS, RP0            ;  Go back to Bank 0

Loop
  movf   PORTA, w			  ;  Simply Transfer PORTA.0 to PORTB.0
  movwf  PORTB

  goto   Loop


 end

Click Here to look at the nineteenth experiment - Current Consumption Check