Confused about clock time/millis() with 8 MHz ATtiny45

Using Arduino Microcontrollers
1

I've been searching and reading for an hour and am still confused about clock time, millis() and delay() while programming the ATtiny45 running @ 8 MHz.

Using Arduino IDE 1.0.1 and my Adafruit USBtinyISP I burned the bootloader to the ATtiny45 after selecting Tools > Board > ATtiny45 @ 8 MHz. I'm powering the chip with 5V.

If I upload the Blink sketch and have a delay(1000) will that actually provide a 2 second delay because the chip is running at 8 MHz and not 16 MHz like an Arduino Uno with ATmega328? I tried eye-balling that blink and it didn't look like 1 second.

I found some posts/blogs while Google searching that talked about CKDIV8 fuse set, but I don't really need to reset the fuses (do I?). I'm fine just multiplying or dividing my values to get the equivalent of millis() and delay() while running at 8 MHz vs. 16 MHz, if I can do that.

Any guidance would be appreciated.

Thanks,
Jake

2

BlueJakester:
If I upload the Blink sketch and have a delay(1000) will that actually provide a 2 second delay because the chip is running at 8 MHz and not 16 MHz like an Arduino Uno with ATmega328?

No. The delay will be approximately one second.

I found some posts/blogs while Google searching that talked about CKDIV8 fuse set, but I don't really need to reset the fuses (do I?).

You already have. That's what burn bootloader does.

3

OK, thanks. I'll try and perform some more accurate testing.