Timer Time: Using Internal ATTiny13A Chip’s Timer “Normal” Mode

Chip’s Internal Timer in ’Normal' mode will count from 0 to 255, set the overflow flag TOV0 to 0 and count again from 0 to 255, set the flag to 0 and so on. 

As usual, I used LED as output indicator on Port B0

We used 1024 for pre-scaler/divider value. Set the TCCR0B to 0000 0101

Note that we have to reset the overflow flag to 1 after timer count reached 255 (and set the flag to 0). 

Oh, by the way, the register/variable/things that count from 0 to 255 is called TCNT0. We didn’t touch it in the code this time, maybe next. 

.include "../tn13Adef.inc"

.def a=r16

.org 0000

init:

    sbi ddrb,0          ; pin b0 output

    ldi a,0b00000101    ; prescaler 1024

    out TCCR0B,a

    

main:

    sbi pinb,0          ; flip the B0 bit

    rcall timer

    rjmp main

timer:

        loop:

    in a,TIFR0          ; wait 

    andi a, 0b00000010  ; (1<<TOV0) is TOV0 still 1 or flagged to 0?

    breq loop

    

    ldi a, 0b00000010   ; set TOV0 to 1 again after flagged

    out TIFR0,a

    

    ret

    

    

Last login: Thu May 28 11:54:47 on ttys001
Nugrohos-MacBook-Air:~ nugroho$ cd attiny13a/timer/
Nugrohos-MacBook-Air:timer nugroho$ avra -o timerNormal.hex timerNormal.s 
AVRA: advanced AVR macro assembler Version 1.3.0 Build 1 (8 May 2010)
Copyright (C) 1998-2010. Check out README file for more info

   AVRA is an open source assembler for Atmel AVR microcontroller family
   It can be used as a replacement of 'AVRASM32.EXE' the original assembler
   shipped with AVR Studio. We do not guarantee full compatibility for avra.

   AVRA comes with NO WARRANTY, to the extent permitted by law.
   You may redistribute copies of avra under the terms
   of the GNU General Public License.
   For more information about these matters, see the files named COPYING.

Pass 1...
Pass 2...
done

Used memory blocks:
   Code      :  Start = 0x0000, End = 0x000B, Length = 0x000C

Assembly complete with no errors.
Segment usage:
   Code      :        12 words (24 bytes)
   Data      :         0 bytes
   EEPROM    :         0 bytes
Nugrohos-MacBook-Air:timer nugroho$ vavrdisasm timerNormal.s.hex 
   0: 9a b8       sbi $17, 0
   2: e0 05       ldi R16, 0x05
   4: bf 03       out $33, R16
   6: 9a b0       sbi $16, 0
   8: d0 01       rcall .+2 ; 0xc
   a: cf fd       rjmp .-6 ; 0x6
   c: b7 08       in R16, 0x38
   e: 70 02       andi R16, 0x02
  10: f3 e9       breq .-6 ; 0xc
  12: e0 02       ldi R16, 0x02
  14: bf 08       out $38, R16
  16: 95 08       ret 
Nugrohos-MacBook-Air:timer nugroho$ 
Nugrohos-MacBook-Air:timer nugroho$ avrdude -p t13 -P usb -c usbasp -B4 -n

avrdude: set SCK frequency to 187500 Hz
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e9007

avrdude: safemode: Fuses OK (H:FF, E:FF, L:6A)

avrdude done.  Thank you.

Nugrohos-MacBook-Air:timer nugroho$ avrdude -p t13 -P usb -c usbasp -B4 -U flash:w:timerNormal.s.hex 

avrdude: set SCK frequency to 187500 Hz
avrdude: AVR device initialized and ready to accept instructions

Reading | ################################################## | 100% 0.00s

avrdude: Device signature = 0x1e9007
avrdude: NOTE: "flash" memory has been specified, an erase cycle will be performed
         To disable this feature, specify the -D option.
avrdude: erasing chip
avrdude: set SCK frequency to 187500 Hz
avrdude: reading input file "timerNormal.s.hex"
avrdude: input file timerNormal.s.hex auto detected as Intel Hex
avrdude: writing flash (24 bytes):

Writing | ################################################## | 100% 0.02s

avrdude: 24 bytes of flash written
avrdude: verifying flash memory against timerNormal.s.hex:
avrdude: load data flash data from input file timerNormal.s.hex:
avrdude: input file timerNormal.s.hex auto detected as Intel Hex
avrdude: input file timerNormal.s.hex contains 24 bytes
avrdude: reading on-chip flash data:

Reading | ################################################## | 100% 0.01s

avrdude: verifying ...
avrdude: 24 bytes of flash verified

avrdude: safemode: Fuses OK (H:FF, E:FF, L:6A)

avrdude done.  Thank you.

Nugrohos-MacBook-Air:timer nugroho$ 

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