Binary Search

By default, the tuner starts from the current value of the DFLLULPDLY register and increments or decrements every reference clock period. This linear search can take up to a maximum of 256 reference clock cycles before lock. To speed up the time to lock, binary search can be enabled by writing one to the Binary Search Enable bit in the Control register (DFLLULPCTRL.BINSE). Binary search takes a maximum of 8 reference clock cycles to lock. After 8 reference clock cycles the tuner will operate in normal linear mode to track any changes in the frequency. Note that neither search algorithm is guaranteed to lock if the target ratio is outside of the oscillator tunable range. Binary search will induce large swings in the oscillator frequency. If this is not desirable, an optional safe mode can be used to mask the output clock until the search is complete. Safe mode is enabled by writing a one to the Safe Mode bit in the Control register (DFLLULPCTRL.SAFE). The binary search is re-triggered if there is a write to DFLLULPDLY. Ondemand or sleep modes will not re-trigger the binary search.