Timer Time: Using Internal ATTiny13A Chip’s Timer, CTC with Automatic Mode

What if we want it to do the task automatically? With neither interrupt routine nor call command?.

We could use CTC mode . The TCNT0 will start counting up, restarted to zero (and generate interrupt) if its value reaches OCR0A value (the compare value we set).

Since, in the matter of talking, the timer has its flag status on pin B0, if we set it as output, we could see the status (high/low, on off) via led connected to it and ground.  

Note that we don’t use ‘interrupt routine’ but the system’s still generate an interrupt.

.include "../tn13Adef.inc"

.def a=r16

.org 0000

init:

sbi ddrb,0              ; pinb as output 

ldi a,0b01000010        ; CTC mode

out TCCR0A,a

ldi r16,0b00000101      ; pre-scaler /1024

    out TCCR0B,a

    ldi a,200                ; compare value

    out OCR0A,a             

loop:

rjmp loop

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