Contradictory Register Diagrams

Other Hardware 3rd Party Boards
1

I was trying to study the structures of the TIFR1 register. So I googled it for its diagram but I found two websites that has information which contradicts one another.

http://web.ics.purdue.edu/~jricha14/Timer_Stuff/TIFR.htm

https://sites.google.com/site/qeewiki/books/avr-guide/timers-on-the-atmega328

Here, at the first link, its written that TOV1 is located at bit2 of TIFR1 register. But at the second link, it is showed that TOV1 is actually the bit0 of TIFR1 register. I think the first website is true as writing bitWrite(TIFR1,2,1) actually resets the TOV1.

What are the register locations that stores the values of OCF2B and OCF1A? Once again, these two websites has contradictory information about their position.

Please let me know the correct answer. Thank You.

2

I was trying to study the structures of the TIFR1 register.

For what processor?

The first reference is for ATmega 16, and the second is for ATmega 328. The organization of TIFR1 is different for the two devices.

You need to use the data sheets from Atmel for the devices you want to study. Don't look at websites. Look at the data sheets.

3

The layout diagram of TIFR1 register of ATmea328 as taken from the ATmega328DataSheet for the Newbie:

The layout diagram has shown the bit-0 as TOV (Timer/Counter OVerflow); it would be nice to see TOV1 instead; however, we will take it for TOV1.

TIFR1 is a contraction for:
T and 1 together form 'TC1 = Timer 1/Counter 1 = Timer/Counter 1'
I for Interrupt
FR for Flag Register

Bit refers to the individual bit (bit-0 = 0, bit-1 =1, ...) of the TIFR1 register
Access refers to the ability for the processor to perform data exchange with the register/bit.
R refers that the MCU (user program) can read this bit.
W refers that the MCU (user program) can write data ( 0 or 1) into this bit.
Reset refers that this bit assumes the stated value (here 0) at reset (cold and hot).
Shade refers to the fact that the bit is physically present, but it is not currently available to the user.

The register layout diagram is missing one important information as to:
Can we perform read/write operation on a single bit of this register? To say it in another way: Is the TIFR1 register byte accessible or bit accessible or both?

The answer can be found in the ATmegaInstructionSet.

it is hoped that the OP (Original Poster) will read the Instruction; he will find the answer of the question stated above; he will analyse the working principle of the bitWrite(TIFR1,2,1) instruction that he has mentioned in his post. The value of the TIFR1 can be seen on the Serial Monitor of the Arduino UNO Kit.

4

writing bitWrite(TIFR1,2,1)

Yeah. that's why you shouldn't do that!
You should do

   bitWrite(TIFR1, TOV1, 1);
//   or
   TIFR1 |= 1<<TOV1;

As others have noted, the first link is NOT for TIFR1 on an ATmega328 at all. It's for TIFR (note the missing "1" at the end) on an ATmega16.
Note that both of those should work whether or not the register is in the bit-addressable register range of the AVR.
They'll either produce an SBI instruction, or a lds/bset/sts sequence, but you won't have to worry about that, because you're using C rather than assembler. There are a couple of very rare registers where you might have to go to special lengths to ensure than an SBI is not used, but that would be in the datasheet rather than the instruction set reference.