Self study Timer0 assessment intro

1
Self study Timer0 assessment intro

• Explain in detail how to use Timer0 module as
  timer.

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What you need to know?

• At least
• Reference Manuals for the mid-range MCU
  FamilySection 11gt study 11.1, 11.2, 11.3, 11.6,
  
• Data sheet PIC16F684gtstudy 5 until 5.1.2
  includedYou are using the C-language, so it is
  not necessary to understand the macro instruction
  in detail.

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At the 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) and (2) (sheet 5 and 6)

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From Reference Manuals for the mid-range MCU
Family (document 33023a)
5
Example (1) code snip polling of the T0IF flag
register

• /
• Example of polling the T0IF flag (on overflow)
• A delay of multi 0.256 msec
• param uns8 multi lt0xFF
• /
• void delayPolling(uns8 multi)
• TMR00 //clear timer
• T0CS0 //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 1256, Fosc/4 1 MHzgt
  3906 KHzgt 0.256 msec
• TMR0 255-multi1 //Explane!
• T0IF0 //clear overflow flag
• while (T0IF!1)/wait loop/ T0IF0

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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 next0 //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 18 4MhzFosc gt
  125 kHzgt 8 micro sec
• TMR01 //compensation for 2 instructions see
  data sheet
• do
• next 125 //8125gt 1 msec
• while (TMR0 ! next) /wait loop/
• milliSec-1

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