Quote Originally Posted by skimask View Post
At 8Mhz, there are 2,000,000 instructions cycles per second.
Assuming a 1:1 prescaler, with an 8 bit counter, you'll get 7812.5 Tmr0 overflow interrupts per second.

256 * .5US = 128 US per overflow!

You're off by 1,000 !
Jeeze! You are right. Sorry, I should have more @ SLEEP myself