A method and external control device for preventing frequency locking in a multi-channel neurostimulation system and external control device is provided. A plurality of pulsed electrical waveforms is provided. Each of the pulsed electrical waveforms has a period and a pulse width. The greatest common divisor of the periods of the pulsed electrical waveforms is computed, and the sum of the pulse widths of the pulsed electrical waveforms is computed. A plurality of timing channels in the neurostimulation system is allowed to be programmed with the pulsed electrical waveforms if the greatest common divisor is equal to or greater than the sum.
