Abstract: A servo pattern writer which may be programmed to write a selected servo pattern for a magnetic disk drive memory is provided. The servo pattern writer includes logic circuitry of which the logic functions and interconnections may be configured as appropriate in response to the configuration program to generate the desired servo pattern.

Abstract: A clock pattern writer for a disk drive, having circuitry to write a preliminary clock pattern having a number of clock pulses approximately equal to a desired predetermined number of clock pulses. A second clock pattern having the predetermined number of clock pulses is written by correcting the preliminary pattern as appropriate to achieve the desired number of clock pulses. In the illustrated embodiment, a phase lock loop generates a source signal in phase with the preliminary clock pattern and correction circuitry repeatedly advances or retards the phase of selected individual pulses of the source signal so that the second clock pattern has the predetermined number of clock pulses. Preferably, phase transients in the clock pattern may be eliminated or reduced by writing a third clock pattern using a phase lock loop locked to the second clock pattern.