Lesson nr.04-Watch-dog timer

Hardware setup:
This example illustrates how the watch-dog timer should not be used. A command used for resetting this timer is intentionally left out in the main program loop, thus enabling the microcontroller to be reset. As a result, the microcontroller will be reset all the time, which is reflected as PORT RB.0~RB.7 LED blinking.
Button S1 and (pull-up) resistance with value of 4.7 K will provide the manual reset mode to the microcontroller.
ICSP connector provides the connection between the programmer (PicKit 2) and microcontroller (PIC16F628A).



Circuit Diagram:
For those who want to build it on their own breadboard or other platform, here is the electronic scheme built in Eagle Cad, free version:

Software:
Here is the C program written for MikroC PRO for PIC 2010 (version v4.15).

/*
'*******************************************************************************
'  Lesson nr.04:
'          Watch-dog timer
'  Written by:
'          Aureliu Raducu Macovei, 2010.
'  Description:
'          This example illustrates how the watch-dog timer should not be used.
'          A command used for resetting this timer is intentionally left out in
'          the main program loop, thus enabling the microcontroller to be reset.
'          As a result, the microcontroller will be reset all the time, which is
'          reflected as PORT RB.0~RB.7 LED blinking.
'  Test configuration:
'    MCU:                        PIC16F628A
'    Test.Board:                 WB-106 Breadboard 2420 dots
'    SW:                         MikroC PRO for PIC 2010 (version v4.15)
'  Configuration Word
'    Oscillator:                 INTOSC:I/O on RA.6, I/O on RA.7
'    Watchdog Timer:             ON
'    Power up Timer:             Disabled
'    Master Clear Enable:        Enabled
'    Browun Out Detect:          Enabled
'    Low Voltage Program:        Disabled
'    Data EE Read Protect:       Disabled
'    Code Protect:               OFF
'*******************************************************************************
*/
void main()                     // Main;
{
 OPTION_REG = 0x0E;             // Prescaler is assigned to timer wdt
                                // (1:4[0x0A];1:8[0x0B];1:16[0x0C];1:32[0x0D];
                                // 1:64[0x0E];1:128[0x0F]);
 asm CLRWDT;                    // Assembly command to reset WDT timer;
 TRISB = 0x00;                  // All port B pins are configured as output;
 PORTB = 0x0F;                  // Initial value of the PORTB register;
 Delay_ms(600);                 // 600ms delay;
 PORTB = 0xF0;                  // Porta B value different from initial;
 while(1);                      // Endless loop. Program remains here until WDT
                                // timer reset the  microcontroller;
 }                              // End.