What are you trying to accomplish here?
I was just trying to give you a hint about the only document I've found about Atmega (8 and 168) pins current limit. If you (or all post readers) find another (from Atmel only, please), let us know.
I've read a lot of warnings here about damaging pins if you draw too much current.
All I did was pointing you to the original source of the info you've read a lot, because I was not sure you've read the datasheet. I think it's important to know where the information comes from.
I don't know anything about PIC, but I'm curious, because you said:
I have experience with PIC chips... They have internal current limiting protection.
and Worapoht said:
and generic PIC Micro never said that it has current limit on pins
but PIC Micro intrinsic had more "drive ability" and overloaded more..
yes, it's may run now but degraded on later days.
Real current-limit had present on some driver IC or some specialize Microcontroller only.. not PIC or AVR
I think Atmega will not get easy damaged with a led over current, but only because the IC is not fragile. But I'm confused about the PIC protection. If it exists or not. I won't search for this now, because I'm not planning on use PICs now. It's just a curiosity.
I realize since it can source 40 mA, I can't connect an LED directly to a pin, but doesn't it have an internal limit like the PIC? I'd expect that I would blow the LED but not damage the MCU.
In the datasheet, I couldn't find any information about over current protection (that doesn't mean it doesn't exist). And more: it only says:
...doesn't say anything other than 40mA is the absolute max current for IO pins
...exceeding any of the specs (such as operating voltage) may damage the chip.
I understand this as: No, there is no over current protection. But this words are not in datasheet. It's my opinion. And I understand it as it's not a good idea to use a led without a current limiter resistor.
So, what is the purpose of your post?
Well, like I said, my post exists only to try to point you a direction, not to give a specific answer. We're human. We can make mistakes. Sorry by the misunderstanding on my post (English is not my native language). I hope you forgive me.
BTW, let me ask you:
We know a led works with a specific voltage (less than 5v. from Arduino) and specific current (less than Atmega pin current limits), that makes necessary to use a current limiter resistor in series with the led to reduce the voltage between anode/cathode and limit the current (it's the First Ohm Law - like Worapoht said). Arduino can be used in many creative ways (artistic, toys, engineering) - but electronics is an exact science (almost ;)). So, why do you want to work with a led without its resistor on Arduino pins?
What is the purpose of your post? Do you want to blow a led?