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On many systems, it is required to continue to push on the panic bar during the countdown period.įlash_bits=lights > 8 /* update lights */ On some systems, an audible countdown announcement accompanies the numeric indicator on the magnetic lock. The alarm is continuous during the countdown. Typically, a numeric indicator on the magnetic lock shows the time remaining.
#PHYSICAL COUNTDOWN TIMERS CODE#
Line 35 case 10 is a shorthand way of saying, if minTens is 10 execute the code and then break out of the switch section. For example line 33 calls the function switch (minTens) which then looks at various cases for the value of minTens (lines 34–44). Lines 31–41 scan the keypad and use the case statement instead of an if statement to determine which key is pressed and stores the number 0–9 in the variable minTens and displays it on the screen. The code following scans for the data, minutes tens, minutes units, seconds tens, and seconds units. Prescaler is / 32 so TMR0 has a pulse rate of 128μs × 32 = 4.096ms.
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Unsigned characters store variables from 0 to 255. Characters need 8 bits of memory and store variables up to ☑28. Line 8 defines the variables as characters. Lines 5 and 6 include the scan and LCD routines in the program. TMR0L=12 //TMR0 overflows in 244 pulses 143. While(INTCONbits.TMR0IF=0) //wait until TMR0L=0, TMR0 interrupt flag=1 142. WriteCmd (CURSOR_RIGHT) // moves cursor right 25. WriteCmd (CURSOR_BLINK) // blinks cursor 24. WriteCmd (FOUR_BIT & LINES_5X7) // sets 5x7 and multiline operation. WriteCmd (0x02) // sets 4bit operation 22. T0CON=0b11010100 //TMR0 on, 8bit timer, clocking on internal clock, prescaler/32. INTCON2bits.RBPU=0 //turns on PORTB pullups 19. PORTB=0b00000000 //turns off PORTB outputs, good start position 18. TRISB=0b00001111 //sets PORTB as all outputs 17.
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PORTA=0b00000000 //turns off PORTA outputs, not required, no outputs 16. #pragma config WDT=OFF, OSC=INTIO2, PWRT=ON, LVP=OFF, MCLRE=OFF 4.Ĭhar secUnit, secTen, minUnit, minTen, result 9. The program for the countdown timer is shown below in Countdown.C 1.