Disc drive with write precompensation using window/pulse timing measurements

A method of measuring spacing between a data pulse and a following edge of a data window in a magnetic system, comprising:

• reading a data signal from a magnetic medium of the magnetic storage system;
• charging a capacitor in response to detection of a data pulse in the data signal;
• converting a voltage on the capacitor into a digital value in response to detection of an edge of a window signal subsequent to the data pulse;
• the data window signal being different from the data signal;
• and
• converting the digital value to a time measurement representative of time between detection of the data pulse and detection of the edge of the data window signal.

An apparatus for providing a time measurement representative of time between a data pulse and an edge of a data window signal generated in a magnetic storage system, comprising:

• a capacitor;
• means for electrically charging the capacitor;
• initiating means, coupled to the means for electrically charging the capacitor, for initiating charging on the capacitor in response to a data pulse in a data signal, the initiating means comprising steering logic responsive to the data pulse and a switch connected to the means for electrically charging the capacitor;
• and
• analog-to-digital converter means connected to the capacitor for converting a voltage level developed across the capacitor into a digital signal representation of the voltage level in response to the edge of a data window signal which is different from the data signal, whereby the digital signal is related to time between the data pulse and the edge of the data window signal.

An apparatus for determining an amount of write precompensation for a magnetic storage medium in a magnetic storage system, comprising:

• a magnetic head for reading information from a surface of the magnetic storage medium and providing an output signal comprising data pulses;
• delay circuitry connected to the magnetic head for delaying data pulses and having a delayed pulse output;
• a window generator circuit connected to the magnetic head and having a data window output;
• enable circuit means connected to data window output and the delayed pulse output for generating an enable signal in response to a delayed data pulse and a data window;
• linear signal generating means connected to the magnetic head for generating a linearly changing signal in response to detection of a data pulse;
• and
• analog-to-digital converter means connected to linear signal generating means and the enable circuit means whereby the linearly changing signal is converted into a digital value in response to the enable signal.

An apparatus for measuring spacing between a data pulse and a following edge of a data window in a magnetic storage system including a magnetic storage media and a magnetic head, comprising:

• a capacitor;
• means coupled to the capacitor for charging the capacitor;
• an analog-to-digital converter connected to the capacitor for converting a voltage on the capacitor to a digital value;
• charge controller means, coupled to the means for charging the capacitor, for triggering charging of the capacitor upon detection of a data pulse;
• and
• delay circuitry coupled between the magnetic head and the charge controller means for delaying data pulses from the magnetic head;
• and
• converter controller means, coupled to the analog-to-digital converter, for triggering conversion of the voltage on the capacitor to the digital value upon detection of an edge of a data window immediately following a delayed data pulse.