TIFR1 not writable on ATMega2560?

Using Arduino Programming Questions
1 
void setup()
{
  Serial.begin(9600);
  Serial.write(TIFR1);
  TIFR1=12;
  Serial.write(TIFR1);
}
void loop()
{
}

As read from the serial port, TIFR1 is 0 both before and after writing it to 12. Why?

2

TIFR is an interrupt flag register.
1 is set when the interrupt condition is met.
Writing 1 there means clearing to 0.
Please refer to the datasheet.

a
a927×660 149 KB

3

So there're no ways to write it to logical one manually?

4

Yes it is.

5

Tell us why you want to do this.

6

Why are you trying to set Bit 3 which is reserved and will always read as 0?

Note: I don't think there is any way to cause a compare match interrupt. You should be able to call the ISR if you want to pretend a match happened.

7

Be careful if you do that. What happens if the interrupt occurs during the "manual" function call? Is the ISR reentrant-safe?

If not surround the manual call with noInterrupts() / interrupts().

8

why the double post?

you already had an answer here

9

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