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The PIC uCs PIC Microcontroller and Embedded Systems Muhammad Ali Mazidi, Rolin McKinlay and Danny Causey Eng. Husam Alzaq The Islamic Uni. Of Gaza 9-1.

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Presentation on theme: "The PIC uCs PIC Microcontroller and Embedded Systems Muhammad Ali Mazidi, Rolin McKinlay and Danny Causey Eng. Husam Alzaq The Islamic Uni. Of Gaza 9-1."— Presentation transcript:

1 The PIC uCs PIC Microcontroller and Embedded Systems Muhammad Ali Mazidi, Rolin McKinlay and Danny Causey Eng. Husam Alzaq The Islamic Uni. Of Gaza 9-1

2 The PIC uCs Chapter 9: PIC18 Timer Programming in Assembly and C PIC Microcontroller and Embedded Systems Muhammad Ali Mazidi, Rolin McKinlay and Danny Causey, February 2007. 9-2

3 The PIC uCs Objective r List the Timers of PIC18 and their associated registers r Describe the various modes of the PIC18 timers r Program the PIC18 timers in Assembly to generate time delays r Program the PIC18 timers in Assembly as event counters 9-3

4 The PIC uCs Outlines r Programming timers 0 and 1 r Counter Programming 9-4

5 The PIC uCs Introduction r PIC18 has two to five timers m Depending on the family number r These timers can be used as m Timers to generate a time delay m Counters to count events happening outside the uC 9-5

6 The PIC uCs Section 9.1: Programming timers 0 and 1 r Every timer needs a clock pulse to tick r Clock source can be m Internal  1/4th of the frequency of the crystal oscillator on OSC1 and OSC2 pins (Fosc/4) is fed into timer m External: pulses are fed through one of the PIC18’s pins  Counter r Timers are 16-bit wide m Can be accessed as two separate reg. (TMRxL & TMRxH) m Each timer has TCON (timer Control) reg. 9-6

7 The PIC uCs Timer0 registers and programming r TMR0L & TMR0H are 8-bit Reg. m MOVWF TMR0L m MOVFF TMR0L, PORTB 9-7

8 The PIC uCs T0CON Reg r Determine the timer operations modes r Example r If T0CON= 0000 1000 m 16-bit m No prescaler m Rising edge 9-8 Figure 9-2. T0CON (Timer0 Control) Register

9 The PIC uCs TMR0IF flag bit r Part of INTCON 9-9 Figure 9-3. INTCON (Interrupt Control Register) has the TMR0IF Flag

10 The PIC uCs Figure 9-4. Timer0 Overflow Flag 9-10

11 The PIC uCs Characteristics and operations of 16-bit mode 1. 16-bit timer, 0000 to FFFFH. 2. After loading TMR0H and TMR0L, the timer must be started. 3. Count up, till it reaches FFFFH, then it rolls over to 0000 and activate TMR0IF bit. 4. Then TMR0H and TMR0L must be reloaded with the original value and deactivate TMR0IF bit. 9-11

12 The PIC uCs Steps to program Timer0 in 16- bit mode to generate time delay 1. Load the value into the T0CON register 2. Load reg. TMR0H followed by reg. TMR0L with initial value 3. Start the timer with instruction BSF T0CON, TMR0ON 4. Keep monitoring the timer flag (TMR0IF) to see if it is raised. 5. Stop the timer 6. Clear the TMR0IF flag 3 7. Go Back to step 2 9-12

13 The PIC uCs Figure 9-5. Timer0 16-bit Block Diagram 9-13

14 The PIC uCs Example 9-3 r A square wave of 50% duty cycle on the PORTB.5 is created r Analyze the program BCF TRISB,5 MOVLW0x08 MOVWFT0CON HERE MOVLW0xFF MOVWF TMR0H MOVLW0xF2 MOVWFTMR0L BCF INTCON, TMR0IF BTGPORTB,5 BSF T0CON, TMR0ON AGAIN BTFSSINTCON, TMR0IF BRAAGAIN BCFT0CON, TMR0ON BRAHERE 9-14 FFF2 FFF3 FFF4 FFFF 0000 TMR0IF=0 TMR0IF=1

15 The PIC uCs Example 9-5 r Calculate the frequency of the wave generated on PIN PORTB 5. BCF TRISB,5 MOVLW0x08 MOVWFT0CON BCF INTCON, TMR0IF HERE MOVLW0xFF MOVWFTMR0H MOVLW-D'48' MOVWFTMR0L CALL DELAY BTGPORTB,5 BRA HERE DELAY BSF T0CON, TMR0ON AGAIN BTFSSINTCON, TMR0IF BRAAGAIN BCF T0CON, TMR0ON BCF INTCON, TMR0IF RETURN 1 1 1 1 2 1 2 1 48 1 1 2

16 The PIC uCs Figure 9-6. Timer Delay Calculation for XTAL = 10 MHz with No Prescaler r General formula for delay calculation m T = 4/(10MHz) = 0.4 usecond 9-16

17 The PIC uCs Example 9-8 r Write a program to generate a square wave with a period of ms on pin PORTB.3 (XALT=10 Mhz) r T = 10 ms r Time delay = 10ms/2 = 5 ms. r We need 5ms/0.4us = 12500 clocks r FFFF - 30D4 +1 =CF2C r TMR0H = CFH r TMR0L= 2CH 9-17

18 The PIC uCs Example 9-8, Cont. BCF TRISB,3 MOVLW0x08 MOVWFT0CON HERE MOVLW0xCF MOVWFTMR0H MOVLW0x2C MOVWFTMR0L BCF INTCON,TMR0IF CALL DELAY BTGPORTB,3 BRA HERE DELAY BSF T0CON,TMR0ON AGAIN BTFSSINTCON,TMR0IF BRAAGAIN BCF T0CON,TMR0ON RETURN 9-18

19 The PIC uCs Example 9-8, Cont. 9-19

20 The PIC uCs Prescaler and generating larger delay r The size of delay depend on m The Crystal frequency m The timer’s 16-bit register. r The largest timer happens when TMR0L=TMR0H=0 r Prescaler option is used to duplicate the delay by dividing the clock by a factor of 2,4, 8,16, 32,64,128,256 m If T0CON=0000 0101, then T = 4*64/f 9-20 XTAL Osc÷ 4÷ 64TMRx

21 The PIC uCs Example 9-13 r Examine the following program and find the time delay in second. r Assume that XALT = 10 MHz. BCF TRISB,2 MOVLW0x05 MOVWFT0CON HERE MOVLW0x01 MOVWFTMR0H MOVLW0x08 MOVWFTMR0L BCF INTCON,TMR0IF CALLDELAY BTGPORTB,2 BRA HERE 9-21

22 The PIC uCs Figure 9-7. Timer0 8-bit Block Diagram 9-22

23 The PIC uCs Figure 9-8. Timer1 High and Low Registers r Can be programmed in 16-bit mode only r It has 2 bytes named as TMR1L and RMR1H r It has also T1CON and TMR1IF r The module incorporates its own low-power oscillator to provide an additional clocking option. r Used as a low-power clock source for the microcontroller in power-managed operation. 9-23

24 The PIC uCs Figure 9-9. Timer1 Block Diagram 9-24

25 The PIC uCs Figure 9- 10. T1CON (Timer 1 Control ) Register 9-25

26 The PIC uCs Figure 9-11. PIR1 (Interrupt Control Register 1) Contains the TMR1IF Flag 9-26

27 The PIC uCs SECTION 9.2: Counter Programming r Used to counts event outside the PIC m Increments the TMR0H and TMR0L registers r T0CS in T0CON reg. determines the clock source, m If T0CS = 1, the timer is used as a counter m Counts up as pulses are fed from pin RA4 (T0CKI) m What does T0CON=0110 1000 mean? r If TMR1CS=1, the timer 1 counts up as clock pulses are fed into pin RC0 9-27

28 The PIC uCs Using external Crystal for Timer1 clock r Timer1 comes with two options, m clock fed into T1CKI T1OSCEN=0 m Clock from a crystal connected to T1OSI- T1OSO (additional) T1OSCEN=1 32 kHz Crystal is connected Used for saving power during SLEEP mode  doesn’t disable Timer1 while the main crystal is shut down 9-28 External Source Internal Source

29 The PIC uCs Example 9-23 r Assuming that clock pulses are fed into pin T0CK1, write a program for counter 0 in 8- bit mode to count the pulses and display the state of the TMR0L count on PORTB. BSFTRISA,RA CLRF TRISB MOVLW0x68 MOVWFT0CON HEREMOVLW0x0 MOVWFTMR0L BCFINTCON,TMR0IF BSFT0CON,TMR0ON AGAIN MOVFF TMR0L,PORTB BTFSSINTCON,TMR0IF BRAAGAIN BCFT0CON,TMR0ON GOTOHERE 9-29

30 The PIC uCs Example 9-24 r Assume that a 1 Hz frequency pulse is connected to input for Timer0(T0CKI) r Write a program to display counter 0 on PORTB, C and D in decimal. r Ser the initial value of TMR0L to -60. NUMEEQU0x00 QUEQU0x20 RMND_LEQU0x30 RMND_MEQU0x31 RMND_HEQU0x32 MYDENEQUD'10' BSF TRISA,RA4 MOVLW0x68 MOVWFT0CON HEREMOVLW0x0 MOVWFTMR0L BCFINTCON,TMR0IF BSFT0CON,TMR0ON 9-30

31 The PIC uCs Example 9-24 AGAINMOVF TMR0L,W CALL BIN_ASC_CON BTFSS INTCON,TMR0IF BRAAGAIN BCFT0CON,TMR0ON GOTOHERE BIN_ASC_CON MOVFFPORTB,WREG MOVWFNUME MOVLWMYDEN CLRFQU D_1INCFQU SUBWFNUME BCD_1 ADDWFNUME DECFQU MOVFFNUME,RMND_L MOVFFQU,NUME CLRFQU D_2INCFQU SUBWFNUM BCD_2 ADDWFNUM DECFQU MOVFFNUME,RMND_M MOVFFQU,RMND_H RETURN 9-31

32 The PIC uCs Example 9-26 r Assuming that clock pulses are fed into pin T0CKI and a buzzer is connected to pin PORTB.1 write a program for counter0 in 8-bit mode to sound the buzzer every 100 pulses BCF TRISB,1 BSF TRISA,4 MOVLW0x68 MOVWFT0CON MOVLW-D'100' MOVWFTMR0L BCF INTCON,TMR0IF BSF T0CON,TMR0ON AGAINBTFSS INTCON,TMR0IF BRAAGAIN BCFT0CON,TMR0ON OVERBTGPORTB,1 CALLDELAY GOTOOVER 9-32

33 The PIC uCs Example 9-27 r Assume that a 1 Hz frequency pulse is connected to input for Timer1(RC0) r Write a program to display the counter values on PORTB and D in decimal. r Initial value=0 r 16-bit and no Prescaler BSF TRISC,RC0 CLRFTRISB CLRFTRISD MOVLW0x02 MOVWFT1CON HEREMOVLW0x0 MOVWFTMR1H MOVLW0x0 MOVWFTMR1L BCFPIR1,TMR1IF BSFT1CON,TMR1ON 9-33

34 The PIC uCs Example 9-27 AGAINMOVFF TMR1H,PORTD MOVFFTMR1L,PORTB BTFSSPIR1,TMR1IF BRAAGAIN BCF PIR1,TMR1ON GOTO HERE 9-34

35 The PIC uCs Chapter 9: Summary r The PIC18 can have up to four or more timers/counters. Depending on the family member r Timers: Generate Time Delays (using Crystal) r Counters: Event counter (using Pulse outside) r Timers are accessed as two 8-bit registers, TMRLx and TMRHx r Can be used either 8-bit or 16-bit r Each timer has its own Timer Control register Next: Chapter 10 PIC18 Serial Port Programming in Assembly and C 9-35

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