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Understanding Timer0 Module in PIC Microcontrollers: A Comprehensive Overview

This presentation covers the Timer0 module in PIC microcontrollers, specifically the PIC16F684. It offers a detailed explanation of how to utilize Timer0 as a timer, including the relevant registers (TMR0, T0CS), the prescaler, and delay ranges. Demonstrations include code snippets for polling the T0IF flag and TMR0 register for creating precise delays. Key limitations and the difference between timer mode and watchdog mode are discussed. The presentation utilizes the Reference Manual for mid-range MCU families, emphasizing practical application in C programming.

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Understanding Timer0 Module in PIC Microcontrollers: A Comprehensive Overview

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  1. Self study assignmentTimer0 Prepare a presentation for 5-10 minutes about the subject Timer. Explain in detail how to useTimer0 module as timer.

  2. What you need to study? At least: • Reference Manuals for the mid-range MCU FamilySection 11=> study 11.1, 11.2, 11.3, 11.6, • Data sheet PIC16F684=>study 5 until 5.1.2 includedYou are using the C-language, so it is not necessary to understand the macro instruction in detail.

  3. Include in your presentation at least the next topics • fig 11.6 (sheet 4) • Limitation • Only the timer mode • Not the Watch dog mode or counter mode • Registers/Bits • TMR0 • T0CS • PSA • T0IF flag • Prescaler • Range of delays • Code snip example (1) (sheet 5)

  4. From Reference Manuals for the mid-range MCU Family(document 33023a)

  5. Example (1)code snippolling of the T0IF flag register /* Example of polling the T0IF flag (on overflow) A delay of multi * 0.256 msec; param uns8 multi <=0xFF */ void delayPolling(uns8 multi) { TMR0=0; //clear timer T0CS=0; //OPTION_REG.5 see data sheet PSA =0; //OPTION_REG.3 see data sheet OPTION_REG &=0b.1111.1000; //bit 2-0 prescaler ??? OPTION_REG |=0b.0000.0111; //bit 2-0 prescaler ??? //prescaler 1:256, Fosc/4 =1 MHz=> 3906 KHz=> 0.256 msec TMR0= 255-multi+1; //Explane! T0IF=0; //clear overflow flag while (T0IF!=1)/*wait loop*/ ; T0IF=0; }

  6. Example (2)code snip polling of the TMR0 register /* * A delay of milliSec msec; * param uns16 milliSec * CC5X compiler C notation */ void delay(uns16 milliSec) { uns8 next=0;//next is a cyclic counter (0-255) TMR0=0; //clear timer T0CS=0; //OPTION_REG.5,see data sheet PSA=0; //OPTION_REG.3,see data sheet OPTION_REG &=0b.1111.1000;//bit 2-0 prescaler OPTION_REG |=0b.0000.0010;//bit 2-0 prescaler //result prescaler 1:8 4Mhz=Fosc => 125 kHz=> 8 micro sec TMR0=1;//compensation for 2 instructions see data sheet do{ next +=125; //8*125=> 1 msec while (TMR0 != next) /*wait loop*/; milliSec-=1; } while(milliSec!=0); }

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