A timer is an 8-bit integer that decrements at a constant rate.

Timers can have two different states, active and inactive. A timer is active whenever its value is above 0, while in this state, the value decrements whenever a ticks occurs until it reaches 0, when it becomes inactive and stops decrementing. On each tick, the value decrements on steps of 1, and they should run at a rate of 60Hz. Such rate needs to configured externally, it is common that emulators tie up this with the display's refresh rate.