This flag can be checked manually, or you can have the timer trigger an interrupt as soon as the flag is set. The timer normally sets a flag bit to let you know an overflow has occurred. The timer increments this counter one step at a time until it reaches its maximum value, at which point the counter overflows, and resets back to zero. The counter register can count to a certain value, depending on its size (usually 8 bits or 16 bits). Timers work by incrementing a counter variable known as a counter register. The LED will blink perfectly on time, regardless of what your main program was just doing How do timers work? With a timer interrupt, you can set up the interrupt, then turn on the timer. If you are not using timers but just conventional code techniques, you’d have to set a variable with the next time the LED should blink, then check constantly to see if that time had arrived. So suppose you have a device that needs to do something –like blink an LED every 5 seconds. Rather than running a loop or repeatedly calling millis(), you can let a timer do that work for you while your code does other things. Timers, like external interrupts, run independently from your main program. When that point arrives, that alert interrupts the microprocessor, reminding it to do something, like run a specific piece of code. Like in real life, in microcontrollers a timer is something you set to trigger an alert at a certain point in the future. This article will discuss AVR and Arduino timers and how to use them in Arduino projects or custom AVR circuits.
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