LOGICIEL EMBARQUE LA GESTION DU COUNTER/TIMER

Transcription

1 LOGICIEL EMBARQUE LA GESTION DU COUNTER/TIMER Finalité Technologie de l Informatique Haute Ecole Namur Liège Luxembourg

2 LA GESTION DU COUNTER/TIMER Un compteur/minuteur (counter/timer) est un périphérique qui permet : De compter des évènements extérieurs: Passages de personnes dans un local, Passage de pièces dans une unité de production De générer une référence de temps (horloge) De générer une interruption après un laps de temps défini Création d un OS (callback function) De chronométrer un temps séparant deux évènements : Mesure de la vitesse d un arbre moteur Mesure de la période d un signal Mesure d un rapport cyclique De générer des signaux MLI (PWM) Commande de moteur, Eclairage 2 Haute Ecole Namur Liège Luxembourg

3 LA GESTION DU COUNTER/TIMER Le PIC 18F46K22 contient : 1 Timer0 (counter / Timer) Mode 8 ou 16 bits Diviseur de fréquence (3 bits) Interruption en overflow 3 Timers (1/3/5) (counter / Timer) Mode 16 bits Source d horloge externe ou interne + Diviseur de fréquence (2 bits) Interruption en overflow Possibilité de compter des évènements externes Base de temps pour les fonctions «Capture/Compare» 3 Timers (2/4/6) (Only Timer) Mode 8 bits Diviseur de fréquence (2 bits) Interruption (TMRx match with Prx) 3 Haute Ecole Namur Liège Luxembourg

4 Overflow Mode 4 Haute Ecole Namur Liège Luxembourg

5 Capture Mode In capture operation, the CCP module copy the contents of a timer into a capture register on an signal edge. 5 Haute Ecole Namur Liège Luxembourg

6 Compare Mode In compare operation, the CCP module compares the contents of a CCPR register with that of Timer in every clock cycle. When these two registers are equal, the associated pin may be pulled to high, or low, or toggled. 6 Haute Ecole Namur Liège Luxembourg

7 Compare Mode 7 Haute Ecole Namur Liège Luxembourg

8 Pulse Width Modulation (PWM) In PWM mode, the CCP module can be configured to generate a waveform with certain frequency and duty cycle. 8 Haute Ecole Namur Liège Luxembourg

9 Pulse Width Modulation (PWM) 9 Haute Ecole Namur Liège Luxembourg

10 Pulse Width Modulation (PWM) 10 Haute Ecole Namur Liège Luxembourg

11 Pulse Width Modulation (PWM) 11 Haute Ecole Namur Liège Luxembourg

12 TIMER0 Can be configured as an 8-bit or 16-bit timer or counter. Can select the internal instruction cycle clock or the T0CKI signal as the clock signal. The user can choose to divide the clock signal by a prescaler before connecting it to the clock input to Timer0. An interrupt may be requested when Timer rolls over from 0xFFFF to 0x0000 The T0CON register controls the operation of Timer0. 12 Haute Ecole Namur Liège Luxembourg

13 TIMER0 13 Haute Ecole Namur Liège Luxembourg

14 TIMER0 14 Haute Ecole Namur Liège Luxembourg

15 TIMER0 15 Haute Ecole Namur Liège Luxembourg

16 TIMER0 16 Haute Ecole Namur Liège Luxembourg

17 TIMER0 17 Haute Ecole Namur Liège Luxembourg

18 TIMER0 Example : Write a subroutine to create a time delay that is equal to 100 ms time value x assuming that the crystal oscillator is running at 32 MHz. Solution : 1.Place the value into the TMR0 high byte and the TMR0L register so that Timer0 will overflow in clock cycles. 2.Choose instruction cycle clock as the clock source and set the prescaler to 16 so that Timer0 will roll over in 100 ms. 3.Enable Timer0. 4. Wait until Timer0 to overflow 18 Haute Ecole Namur Liège Luxembourg

19 TIMER0 Langage C 19 Haute Ecole Namur Liège Luxembourg

20 TIMER1/3/5 Is a 16-bit timer/counter. An interrupt may be requested when Timer1 rolls over from 0xFFFF to 0x0000. Timer1/3/5 can be reset when the CCP module is configured to compare mode to generate a special event trigger. Timer1/3/5 operation is controlled by the T1CON register. Timer1/3/5 can be configured to use the oscillator connected to the T1OSO and T1OSI pins. The Timer1/3/5 oscillator is primarily intended for a 32 KHz crystal. Timer1/3/5 can be used to create time delays and measure the frequency (period) of an unknown signal. 20 Haute Ecole Namur Liège Luxembourg

21 TIMER1/3/5 «Gate Mode» 21 Haute Ecole Namur Liège Luxembourg

22 TIMER1/3/5 «Gate Mode» 22 Haute Ecole Namur Liège Luxembourg

23 TIMER1/3/5 Timer Mode 23 Haute Ecole Namur Liège Luxembourg

24 TIMER1/3/5 Counter Mode 24 Haute Ecole Namur Liège Luxembourg

25 TIMER1/3/5 Example :Use Timer0 as a timer to create a one-second delay and use Timer1 as a counter to count the rising (or falling) edges of an unknown signal (at the T1CKI pin) arrived in one second which would measure the frequency of the unknown signal. Write a program to implement this idea assuming that the PIC18 MCU is running with a 32MHz crystal oscillator. Solution: A one-second delay can be created by placing 10 in cx and calling the delay function in Example 2. Timer1 should be configured as follows: 16-bit mode prescaler value set to 1 disable oscillator do not synchronize external clock input select external T1CKI pin signal as the clock source Timer1 may overflow many times in one second The user must enable the Timer1 overflow interrupt and keep track of the number of times that it interrupts. 25 Haute Ecole Namur Liège Luxembourg

26 TIMER1/3/5 The setting of Timer1 interrupt is as follows: Enable priority interrupt Place Timer1 interrupt at high priority Enable only Timer1 roll-over interrupt Langage C 26 Haute Ecole Namur Liège Luxembourg

27 TIMER1/3/5 27 Haute Ecole Namur Liège Luxembourg

28 TIMER2/4/6 8-bit timer TMR2 and 8-bit period register PR2. TMR2 is counting up and comparing with PR2 in every clock cycle. When TMR2 equals PR2, the TMR2 is reset. A postscaler is applied to the reset signal to generate the TMR2 interrupt. The TMR2 output is fed to the synchronous serial port module. The operation of Timer2 is controlled by T2CON register. 28 Haute Ecole Namur Liège Luxembourg

29 TIMER2/4/6 29 Haute Ecole Namur Liège Luxembourg

30 TIMER2/4/6 30 Haute Ecole Namur Liège Luxembourg

31 TIMER2/4/6 Example : Assume that the PIC18F46k22 is running with a 32 MHz crystal oscillator. Write an instruction sequence to generate periodic interrupts every 8 ms with high priority using Timer2. Solution: By setting the prescaler and postscaler to 16 and loading 249 into the PR2 register, Timer2 will generate periodic interrupt every 8 ms: 31 Haute Ecole Namur Liège Luxembourg

32 LA GESTION DU COUNTER/TIMER Le microcontrôleur est cadencé à une horloge de 1 MHz. Configurer les bits des registres appropriés qui permettent de générer une interruption toutes les 200 ms. Les bits des registres liés à la gestion des interruptions ne sont pas à considérer ici. Ecrire suivant le format xxxxbits.yyyyy = (1 ou 0)) 32 Haute Ecole Namur Liège Luxembourg

33 Bibliographie 33 Haute Ecole Namur Liège Luxembourg