A sleep timing system for a wireless mobile station includes a circuitry that enables the mobile station to enter a low-power mode immediately upon command. The circuitry transitions the mobile station into the low-power mode without waiting for a next pseudo-random noise (PN) sequence roll boundary. The timing system includes a counter, a wakeup time register, and a sleep timer. The counter receives a PN sequence and estimates a number of clock cycles to the next PN sequence roll boundary. The wakeup time register may be set with a sleep time value in terms of number of PN roll boundaries. The register is provided with a new sleep time value that includes the number of clock cycles to the next PN sequence roll boundary.